Ukraine on Saturday said Russian forces were making a "rapid retreat" from northern areas around the capital Kyiv and the city of Chernigiv as the Red Cross prepared for a fresh evacuation effort from the besieged southern port of Mariupol.
Russian forces now appear to be focusing attacks in the east and south, a day after thousands of people from Mariupol and surrounding Russian-held areas escaped in a convoy of buses and private cars.
"Russia is prioritising a different tactic: falling back on the east and south," Ukrainian presidential adviser Mykhaylo Podolyak said on social media.
He said that, while Russian forces appeared to be pulling back from Kyiv and Chernigiv, their aim was to "control a vast stretch of occupied territory and set up there in a powerful way".
"Without heavy weapons we won't be able to drive (Russia) out," he said.
President Vladimir Putin ordered Russian tanks into Russia's pro-Western neighbour on February 24 and Ukraine estimates 20,000 people have been killed in the war so far.
More than 10 million have had to flee their homes.
- Journalist killed 'with two shots' -
Pope Francis spoke of "icy winds of war" again sweeping over Europe as he brought up the conflict at the outset of his trip to Malta on Saturday.
"Once again, some potentate, sadly caught up in anachronistic claims of nationalist interests, is provoking and fomenting conflicts," the pope said.
A visit to the Ukrainian capital was still on the table," he added.
In Kyiv, the government confirmed that the body of a well-known photographer, Maks Levin, had been found near a village in the region around the capital that had been caught up in the fighting.
"According to preliminary information, unarmed Maxim Levin was killed by servicemen of the Russian Armed Forces with two shots from small fire arms," prosecutors said in a statement on Telegram.
Levin, a 40-year-old father of four, had been reported missing on March 13 and the body was found near Guta Mezhygirksa on April 1, officials said.
The NGO Reporters Without Borders said six journalists have been killed in the conflict so far, adding: "Targeting journalists is a war crime".
The International Criminal Court has already opened a probe into possible war crimes in Ukraine.
Former war crimes prosecutor Carla Del Ponte said in an interview published on Saturday that the ICC should issue an arrest warrant for Putin.
"Putin is a war criminal," Del Ponte, who came to prominence investigating war crimes in Rwanda and the former Yugoslavia, told the Le Temps daily.
- 'Our city doesn't exist anymore' -
Even as Russia consolidates its hold on southern and eastern areas of the country, Mariupol has remained an important Ukrainian hold-out.
The city has suffered weeks of Russian shelling, with at least 5,000 residents killed, according to local officials.
The estimated 160,000 who remain face shortages of food, water and electricity.
"We have managed to rescue 6,266 people, including 3,071 people from Mariupol," Ukrainian President Volodymyr Zelensky said in a video address earlier on Saturday.
Dozens of buses carrying Mariupol residents who had escaped the city earlier arrived on Friday in Zaporizhzhia, 200 kilometres (120 miles) to the northwest, according to an AFP reporter on the scene.
The buses carried people who had been able to flee Mariupol to Russian-occupied Berdiansk.
"We were crying when we reached this area. We were crying when we saw soldiers at the checkpoint with Ukrainian crests on their arms," said Olena, who carried her young daughter in her arms.
"My house was destroyed. I saw it in photos. Our city doesn't exist anymore."
The International Committee of the Red Cross (ICRC) said its team headed to Mariupol to try and conduct an evacuation but was forced to turn back Friday after "arrangements and conditions made it impossible to proceed".
The ICRC said its team left on Saturday bound for Mariupol to make another attempt.
- New US aid -
Peace talks between Kyiv and Moscow resumed via video on Friday, but the Kremlin warned that what it described as a helicopter attack on a fuel depot inside Russia would hamper negotiations.
The air strike hit energy giant Rosneft's fuel storage facility in Belgorod, 40 kilometres from the Ukraine border.
Kyiv would not be drawn on whether it was behind the attack.
Zelensky meanwhile repeated his plea for the West to provide greater military support.
"Just give us missiles. Give us airplanes," he told Fox. "You cannot give us F-18 or F-19 or whatever you have? Give us the old Soviet planes. That's all... Give me something to defend my country with."
The Pentagon later said it was allotting $300 million in "security assistance" to bolster Ukraine's defence capabilities, adding to the $1.6 billion Washington has committed since Russia invaded in late February.
- 'Where roses used to bloom' -
Civilians have trickled out of devastated areas after arduous and daring escapes.
Three-year-old Karolina Tkachenko and her family walked an hour through a field strewn with burnt-out Russian armoured vehicles to flee their village outside Kyiv.
"The shops are closed, there's no delivery of supplies. The bridge is also blown up, we can't go for groceries through there," said Karolina's mother Karina Tkachenko.
In Mariupol, Viktoria Dubovytskaya, who had sheltered in the theatre where 300 people are feared to have been killed in Russian bombardments, said she only grasped the extent of the destruction as she fled.
Bodies lay in the rubble and small wooden crosses were planted in the ground, she told AFP.
"When people find their loved ones, they just bury them wherever they can. Sometimes where roses used to bloom," she said.
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ROSNEFT