The bodies of at least 20 civilian men have been found lying strewn across the street in the town of Bucha, northwest of Kyiv

Ukraine continues to present a "significant challenge" to Russian air and missile operations, leaving Russian aircraft vulnerable to short and medium range air defense systems, the United Kingdom's Ministry of Defense said Sunday.

"Russia’s inability to find and destroy air defence systems has seriously hampered their efforts to gain broad control of the air, which in turn has significantly affected their ability to support the advance of their ground forces on a number of fronts," the ministry wrote in a defense intelligence update posted on Twitter.

The ministry also reported a concentration of Russian air activity towards south eastern Ukraine, "likely a result of Russia focusing its military operations in this area," it said.

Russian naval forces continued to prevent Ukrainian resupply by sea with a "distant blockade" of the Ukrainian coast in the Black Sea and Sea of Azov, the ministry said, though an amphibious landing from Russian forces was likely to be "increasingly high risk" due to Ukrainian preparations.

Reported mines within the Black Sea also "pose a serious risk" to maritime activity, the ministry said, adding that although the origin of such mines remains unclear and disputed, "their presence is almost certainly due to Russian naval activity."

Russian missile strikes hit Ukraine's southern city of Odesa Sunday morning local time, according to the city council. 

“Odesa was attacked from the air. Some of the missiles were downed by our air defense system. In some districts fire has broken out,” the Odesa City Council posted to its official Telegram account.

A fuel depot in the Ukrainian city of Odesa is burning Sunday morning, according to a CNN team on the scene, with one witness telling CNN they heard six explosions at the fuel depot before sunrise.

Some context: The coastal city of Odesa has been a place of relative calm during the Russian invasion and a haven for displaced Ukrainians from areas that have seen the worst fighting. But Odesa has been bracing for a Russian attack for weeks, with its city center full of anti-tank barricades to fortify against an invasion. 

The heartbreaking video looks just like the pictures western TV viewers are getting from the war in Ukraine: a grandmother, bundled up in a thick jacket against the cold, stands weeping in front of her wooden house that's smoldering from a rocket that hit her village. “They destroyed everything!” she cries. “Nothing is left.”

But this is the Russian government-controlled TV channel Rossiya24 and, in this report, the soldiers attacking her village are Ukrainian, not Russian. The Russian correspondent calls them “nationalists.” Other reports on the channel call them “neo-Nazis,” “fascists,” or “drug addicts” who use civilians as “human shields.”

Almost all reports of the conflict are from the breakaway Donbas region in Ukraine’s east, specifically the two self-proclaimed “people’s republics” of Donetsk and Luhansk, primarily Russian-speaking entities that Russia recognized as independent statelets on February 21.

On Russian broadcasts, the war in the rest of Ukraine, the war most people around the world are witnessing, is largely ignored – the wreckage of Mariupol left in the wake of Russian bombing; the charred skeletons of houses and buildings in Kharkiv, Chernihiv, Kherson, Zhytomyr and other towns decimated by Russian airstrikes; residential neighborhoods in the capital Kyiv, along with their shellshocked, bleeding residents fleeing Russian shelling – almost none of this is shown on Russian TV. When it is, it’s blamed of course on Ukrainian forces. There is also no accurate coverage of the recent military setbacks suffered by the Russian military.

In an Orwellian touch, the conflict in Ukraine can be called only a “special military operation.” Under a law passed on March 4, it’s illegal to call the war a “war,” or to describe it as an “attack” or “invasion.” Violators can be punished with up to 15 years in prison, as can news organizations that disseminate anything deemed “fake news” about the “operation” or the Russian military.

Read the full analysis here.

A fuel depot in the Ukrainian city of Odesa is burning Sunday morning, according to a CNN team on the scene.

One witness told CNN they heard six explosions at the fuel depot before sunrise.

Multiple witnesses told CNN they had seen drones in the skies around the area over the past two days.

Video taken by CNN shows plumes of thick black smoke rising to the air from the fuel depot which sits next to a railway track. The plumes could be seen for miles in the distance. The CNN team heard no air raid sirens.

At least one secondary explosion was heard as firefighters were trying to control the blaze. It is unclear whether there have been casualties.

Civilian bodies were found littering the streets of a Ukrainian town northwest of Kyiv following the withdrawal of Russian forces, according to images released by AFP on Saturday – the latest horrifying mark of the mounting civilian toll of Russia’s brutal assault on Ukraine.

The Russian withdrawal comes as Moscow attempts to shift its focus to eastern Ukraine and away from the areas around Kyiv, where Russian forces have faced fierce Ukrainian resistance. Ukraine's deputy defense minister said Saturday that the Kyiv region had been "liberated" from Russian forces.

As day breaks on Sunday in Ukraine, these are the latest developments in the war:

Horrors of occupation: The bodies of at least 20 civilian men have been found lying strewn across the street in the town of Bucha, northwest of Kyiv following the withdrawal of Russian forces in images released by AFP on Saturday. At least one corpse can be seen with his hands tied behind his back. The Mayor of Bucha, Anatoliy Fedoruk, told Reuters Saturday the civilians had been executed by retreating Russian forces.

Shift to the east: Russia has revised its Ukraine war strategy to focus on taking control of the Donbas and other regions in eastern Ukraine with a target date of early May, according to several US officials familiar with the latest US intelligence assessments. A Ukrainian presidential adviser warned on Saturday that fighting in the days ahead "will not be easy" in those regions.

Pressure on Putin: Russian President Vladimir Putin is under pressure to demonstrate he can present a victory as heavy setbacks mount up, and eastern Ukraine is where he is most likely to achieve that, US officials say. US intelligence intercepts suggest Putin is focused on celebrating some kind of “Victory Day” on May 9, a prominent holiday on the Russian calendar marking the Nazi surrender in World War II.

Diplomatic potential: A member of the Ukrainian negotiating team in talks with Russia, said Saturday that the Russian side had responded positively to Ukrainian positions on several issues and there was a possibility of "direct consultations" between Ukrainian President Volodymyr Zelensky and Russian leader Vladimir Putin in the future.

Further evacuations: More than 4,000 Ukrainian civilians were able to flee via evacuation corridors on Saturday, according to the country's deputy prime minister. A renewed attempt by the International Committee for the Red Cross to reach Mariupol is expected to continue Sunday.

Tank transfer: The US is expected to help facilitate the transfer of Soviet-era tanks "within days" to Ukraine, according to a source familiar with the plan. Ukrainian presidential adviser Mykhailo Podolyak earlier on Saturday called on the US and its allies to deliver heavier weaponry to Ukraine.

The bodies of at least 20 civilian men have been found lying strewn across the street in the town of Bucha, northwest of Kyiv following the withdrawal of Russian forces from the area in shocking images released by AFP on Saturday. 

The dead, all in civilian clothing, are found in a variety of awkward poses, some face down against the pavement, others facing upwards with mouths open.  

"Three of them are tangled up in bicycles after taking their final ride, while others, with waxy skin, have fallen next to bullet-ridden and crushed cars," according to AFP journalists who accessed the town after it had been cut off for nearly a month.

One corpse can be seen with his hands tied behind his back with a white cloth.

The Mayor of Bucha, Anatoliy Fedoruk, said the dead civilians had received inhumane treatment at the hands of Russian forces.  

"Corpses of executed people still line the Yabluska street in Bucha. Their hands are tied behind their backs with white 'civilian' rags, they were shot in the back of their heads. So you can imagine what kind of lawlessness they perpetrated here," Fedoruk told Reuters on Saturday.  

Ukrainian presidential adviser Mykhailo Podolyak said the bodies of the men found with hands tied, "were shot dead by Russian soldiers," in a tweet on Saturday. 

Podolyak added, "these people were not in the military. They had no weapons. They posed no threat. How many more such cases are happening right now in the occupied territories?"

CNN has not been able to independently confirm the details around the men's deaths.

Russian forces withdrew from several towns near Kyiv in recent days after Moscow's bid to encircle the capital failed, with Ukraine declaring that Bucha had been "liberated."

David Arakhamia, a member of the Ukrainian negotiating team in talks with Russia, said the Russian side has responded positively to Ukrainian positions on several issues and there is a possibility of "direct consultations" between Ukrainian President Volodymyr Zelensky and Russian President Vladimir Putin, something he said had been facilitated in part by Turkish President Recep Tayyip Erdogan. 

Ukrainian officials have outlined their vision of a roadmap to a potential truce, which would include possible neutral status for Ukraine backed by a broad alliance of security guarantors.

The status of Crimea -- annexed by Russia from Ukraine in 2014 -- has been a sticking point in potential negotiations between Ukraine and Russia. Ukraine and most of the international community consider the peninsula to be illegally occupied. The Kremlin consistently says the status of Crimea is settled. 

The Ukrainian side said there had been agreement to suspend negotiations on the status of Crimea for 15 years, but the Russian side has not confirmed, and the Kremlin has publicly reiterated its position Crimea is part of Russia.

Dmytro Kuleba, Ukraine’s foreign minister, said there was no official confirmation of those positions in writing, according to Arakhamia.

However, Arakhamia added: "Orally, as of yesterday, in a video conference, we heard that the Russian side does not object to such [Ukrainian] positions."

Arakhamia held out the possibility of a meeting between Putin and Zelensky, saying, "The drafts of the documents were sufficiently developed to hold direct consultations between the two leaders, the presidents of Ukraine and the Russian Federation. Therefore, our task now is to quickly prepare the final stage not of the document itself, but of the issues we have already touched upon, and to prepare for a possible meeting of the presidents."

Arakhamia added: "Yesterday, Mr. Erdogan called both us and Vladimir Putin. He also allegedly confirmed for his part they are ready to organize a meeting in the near future. Neither the date nor the place is known. But we believe that with a high probability it will be in Istanbul or Ankara, that is, in Turkey."

The possibility of a role for China as a potential security guarantor for Ukraine appears to be credible, according to Arakhamia. 

Asked about the status of talks with China on the matter, Arakhamia said: "We are negotiating through diplomatic channels. The state of negotiations with China is probably the least ready compared to the countries that are now actively helping us, and we keep in touch twice a day. With China, it's getting a little harder."