As news spread of a successful evacuation operation from the besieged Azovstal steel plant in Mariupol, the deputy commander of the Azov battalion, Svyatoslav Palamar, said there was little reason to celebrate.

“Not enough is being done to try and evacuate wounded soldiers,” Palamar said, speaking at a press conference at the plant, which is surrounded by Russian forces.

Ukraine's Deputy Prime Minister Iryna Vereshchuk said Saturday the first stage of the rescue operation had concluded and all civilians had been evacuated from the steel plant. Another 173 people were rescued Sunday from Azovstal and surrounding Mariupol, according to the local city council.

But Palamar said some civilians might still be trapped under the rubble of ruined shelters and that many bodies of deceased troops and civilians remain uncollected on the plant's territory.

More than 25,000 people, most of them civilians, have been killed in Mariupol, according to Azov commanders. Half of all Russian bombardment and shelling in Ukraine was aimed at Mariupol, the battalion commanders said, adding that the city was shelled 150 times a day on average.

Russia has lost about 2,500 troops, with a further 500 wounded and over 60 destroyed tanks, in the city, Azov officials claimed. Yet the unblocking of Mariupol by military means remains difficult due to the lack of heavy weapons, Ukrainian President Volodymyr Zelenskyy said during a joint press conference with Canadian Prime Minister Justin Trudeau in Kyiv on Sunday.

Russia continued over the weekend to shell Ukrainian cities. Zelenskyy said Russians have “celebrated” the Day of Remembrance and Reconciliation on May 8 by launching nine missile strikes against Odessa. Zelenskyy spoke at a press briefing in Kyiv held after his talks with visiting Croatian Prime Minister Andrej Plenkovic. The Ukrainian President also met the head of the German parliament, Baerbel Bas, on Sunday. The two leaders spoke about how “German leadership in the European Union” can help Ukraine, Zelenskyy said in his nightly address on Sunday.

Ukrainian Foreign Minister Dmytro Kuleba tweeted Sunday that Berlin made a mistake by prohibiting Ukrainian symbols and flags at rallies during events on May 8-9.

“It's deeply false to treat them equally with Russian symbols,” Kuleba wrote, adding that “taking the Ukrainian flag away from peaceful protestors is an attack on everyone who now defends Europe and Germany from Russian aggression with a flag in their hands.”

On Monday, as Ukraine celebrated the Day of Victory over Nazism in World War II, Zelenskyy said that the ongoing conflict was “not a war of two armies. This is a war of two worldviews.”

Russian missiles are trying to destroy Ukrainian philosophy, Zelenskyy said, because it "scares them.”

“We are free people who have their own path,” the president said. “Today we are waging war on this path and we will not give anyone a single piece of our land.”

-ABC News' Edward Szekeres, Fidel Pavlenko, Irene Hnatiuk, Max Uzol and Uliana Lototska

Canadian Prime Minister Justin Trudeau visited Ukraine on Sunday and toured devastated areas in and around Kyiv with Ukrainian President Volodymyr Zelenskyy.

During a joint news conference, Trudeau pledged Canada's continuing support for Ukraine and condemned Russian President Vladimir Putin for atrocities he alleged Russian forces are responsible for in Ukraine.

"It is clear that Vladimir Putin is responsible for heinous war crimes," Trudeau said. "We will continue to do the work of being there for you with whatever we can, whatever you need."

Trudeau announced that Canada is sending additional military support to Ukraine, including drone cameras, satellite imagery, small arms and ammunition.

The prime minister also said Canada will impose new sanctions on 40 Russian individuals he alleged are complicit in Putin's war.

"And we're bringing forward new sanctions on 40 Russian individuals and five entities, oligarchs and close associates of the regime in the defense sector, all of them complicit in Putin's war," Trudeau said.

Trudeau also announced that all trade tariffs on Ukrainian imports to Canada will be lifted for the next year and that Canada is donating CA$25 million, or about US$19.3 million, to the U.N. World Food Program, which is providing emergency food assistance to people in Ukraine.

Trudeau said that he and Larissa Galadza, Canada's ambassador to Ukraine, raised the Canadian flag at the country's embassy in Kyiv on Sunday to signal its reopening. He called the move an "important symbol not just of Canada's steadfast friendship with Ukraine, but of the incredible resilience and heroism of the Ukrainian people, who ensured that this city did not fall."

-ABC News' Christine Theodorou

Pope Francis on Sunday prayed for peace in Ukraine, entrusting to the Virgin Mary the ''sufferings and tears of the Ukrainian people."

''In front of the war's madness, let us please continue to pray the rosary for peace every day," the pope told thousands of people gathered in the Vatican's St. Peter's Square for his weekly address and blessing.

For several Sundays in a row the pope has led prayers for peace in Ukraine and has condemned the Russian invasion of the country, calling the act of war "senseless" during an Easter Sunday Mass last month.

The pontiff also prayed for the victims of an apparent gas explosion on Friday at the Hotel Saratoga in Havana, Cuba. At least 26 people were killed in the blast at the popular hotel and around 70 people were injured.

U2's frontman Bono and lead-guitarist The Edge surprised fans in Kyiv on Sunday by performing an impromptu concert in the Ukrainian capital's central metro station.

The two Irish rockers delivered a nearly hour-long set at the Khreshchatyk Metro Station, Kyiv's busiest metro station, as several dozen fans watched.

"The people of Ukraine are not just fighting for your own freedom, you're fighting for all of us who love freedom," Bono told the crowd between songs.

The musicians were joined on one of the station's platforms by Taras Topolia, frontman of Ukrainian pop rock band Antytila. Topolia presented Bono with a piece of shrapnel he said was the remains of a missile that struck near the base in Kyiv where he is currently serving in the Ukrainian Army.

Russian forces have carried out five strikes targeting Ukraine railway stations, according to the head of the state-run Ukrainian railways, Oleksandr Kamyshin.

The hardest hit were the towns of Zhmerynka and Kozyatyn, where five people were killed and 18 were injured, according to Serhii Borzov, the head of the Vinnytsia regional military administration.

No casualties were reported in the other railway strikes, which were in the Lviv, Rivne and Zhytomyr regions, officials said.

-ABC News' Natalya Kushnir, Fidel Pavlenko and Christine Theodorou