San Francisco Frontiers - Ukraine battles to hold eastern bastions as US First Lady visits

Kyiv's allies lent their support, with US First Lady Jill Biden and Canadian Prime Minister Justin Trudeau making unannounced visits to Ukraine, and G7 leaders due to join President Volodymyr Zelensky on a video call.

But fierce fighting continued on the ground. Shelling and missile strikes have intensified in the build up to the World War II anniversary, and rescuers are searching for 60 Ukrainian civilians feared killed in the bombing of a village school.

Zelensky marked a day commemorating the end of the 1939-1945 war by comparing Ukraine's battle for national survival to the region's war of resistance against its former Nazi occupiers.

"Decades after World War II, darkness has returned to Ukraine, and it has become black and white again," Zelensky said, in a monochrome social media video shot against the backdrop of a bombed out apartment block.

"Evil has returned, in a different uniform, under different slogans, but for the same purpose," he warned, trying to turn Russia leader President Vladimir Putin's "anti-Nazi" rhetoric back on itself.

Russia, meanwhile, was gearing up for a Victory Day parade designed to associate the invasion of its neighbour with the national pride felt over the Soviet Union's defeat of Germany.

"Today, our soldiers, as their ancestors, are fighting side by side to liberate their native land from the Nazi filth with the confidence that, as in 1945, victory will be ours," Putin said.

Zelensky was also to meet G7 leaders via video conference to discuss the crisis, and European diplomats will meet again next week to hammer out the details of their latest sanctions package against Moscow.

The US first lady met her Ukrainian counterpart Olena Zelenska at a school sheltering civilians, including children displaced by the conflict, near Ukraine's border with Slovakia.

"I wanted to come on Mother's Day," Biden told reporters.

"I thought it was important to show the Ukrainian people that this war has to stop and this war has been brutal and that the people of the United States stand with the people of Ukraine."

Separately, Canadian leader Trudeau visited Irpin, a suburb on the northwest edge of Kyiv that was the scene of heavy fighting in the early weeks of the conflict.

Local mayor Oleksandr Markushyn, posted pictures on social media and said Trudeau "came to Irpin to see with his own eyes all the horror that the Russian occupiers had done to our city."

On the ground, the key battles were being fought in Ukraine's east.

- Tunnel network -

Civilians have now been evacuated from Mariupol's Azovstal steelworks, leaving a small force of defenders holed up in its sprawling network of underground tunnels and bunkers.

The complex -- the final pocket of Ukrainian resistance in the port city -- has taken on a symbolic value.

"We, all of the military personnel in the garrison of Mariupol, we have witnessed the war crimes performed by Russia, by the Russian army. We are witnesses," said Ilya Samoilenko, an intelligence officer with the far-right Azov regiment, which is defending the steelworks.

"Surrender is not an option because Russia is not interested in our lives," he said.

Taking full control of Mariupol would also allow Moscow to create a land bridge between the Crimean peninsula, which it annexed in 2014, and regions run by pro-Russian separatists in the east.

In one of those regions, Lugansk, Ukrainian forces are now mounting a last ditch defence of the city of Severodonetsk, formerly an industrial city of 100,000 people, now Russia's next target.

In the same region, governor Sergiy Gaiday said 60 civilians were feared dead after a school in the village of Bilogorivka was hit in an air strike.

"The bombs fell on the school and unfortunately it was completely destroyed. There were a total of 90 people, 27 were saved," he said on Telegram.

"Sixty people who were in the school are very probably dead."

Rescuers could not work overnight because of a threat of new strikes, but resumed their work on Sunday.

- 'Filtration camps' -

Rescuers were also looking for survivors in the neighbouring village of Shepilivka after a strike hit a house where 11 people were sheltering in the basement, Gaiday said.

Civilians who escape Mariupol describe passing through Russian "filtration" sites where several evacuees told AFP they were questioned, strip-searched, fingerprinted, and had their phones and documents checked.

"They asked us if we wanted to go to Russia... or stay and rebuild the city of Mariupol," said Azovstal evacuee Natalia, who spoke on condition that her full name not be published.

"But how can I rebuild it? How can I return there if the city of Mariupol doesn't exist anymore?"

Russia's campaign has run into tough resistance -- and galvanised Kyiv's Western allies to impose potentially crippling sanctions on the Russian economy and Putin's inner circle.

burs-dc/gw

D.Robinson--SFF