(NewsNation) — The Russian invasion of Ukraine entered its third week Thursday with talks between the two stalling despite thousands of people killed, millions attempting to flee and many more fortifying in besieged cities under relentless bombardment.

At least 549 civilians are confirmed to have been killed in Ukraine since Russian troops invaded on Feb. 24, and another 957 wounded, although the true numbers are probably “considerably higher”, a U.N. monitoring mission said on Thursday.

Vice President Kamala Harris embraced calls for an international war crimes investigation of Russia over its invasion of Ukraine and the bombing of civilians.

Speaking Thursday in Warsaw, Harris expressed outrage over the bombing of the maternity hospital on Wednesday and scenes of bloodied pregnant women being evacuated.

“Absolutely there should be an investigation, and we should all be watching,” Harris said.

Standing alongside Harris, Polish President Andrzej Duda said, “It is obvious to us that in Ukraine Russians are committing war crimes.”

Meanwhile, talks in Turkey between the foreign ministers of Russia and Ukraine failed to bring any respite in the conflict.

Ukrainian Foreign Minister Dmytro Kuleba said he had secured no promise from Russian Foreign Minister Sergei Lavrov to halt firing so aid could reach civilians, including Kyiv’s main humanitarian priority — evacuating hundreds of thousands of people trapped in the besieged port of Mariupol.

Lavrov showed no sign of making any concessions, repeating Russian demands that Ukraine be disarmed and accept neutral status. He said Kyiv appeared to want meetings for the sake of meetings and blamed the West for intensifying the conflict by arming its neighbor.

The talks are the first high-level discussions between the two countries since Russia invaded Ukraine on Feb. 24.

NATO member Turkey, which has cultivated close ties with both Russia and Ukraine, is trying to balance relations with both nations. It has positioned itself as a neutral party, seeking to facilitate negotiations between the warring sides.

The latest round of talks comes after Russia was accused of an airstrike attack on a Mariupol hospital.

The attack wounded at least 17 people, including women waiting to give birth and doctors, and buried children in the rubble, despite a ceasefire deal for people to flee the city.

Russia’s Defence Ministry denied having bombed the hospital, accusing Ukraine of a “staged provocation” there.

Bombs also fell on two hospitals in another city west of the capital Kyiv. The World Health Organization confirmed 18 attacks on medical facilities since the Russian invasion began.

The attack in Mariupol drew strong condemnations from countries around the world.

James Heappey, Britain’s armed forces minister, called the attack a war crime and warned President Vladimir Putin that using chemical weapons in Ukraine could draw “an international response.”

He said whether it was “indiscriminate” fire into a built-up area or a deliberate targeting, “It is a war crime.”

Canadian Prime Minster Justin Trudeau said on Thursday that Putin had made a choice to “specifically target civilians” and any further targeting of civilians in Ukraine is going to be met with the “severest of responses.”

“Putin’s callous disregard for human life is absolutely unacceptable. It is very clear that he has made the choice to specifically target civilians now,” Trudeau told reporters in Warsaw.

Despite no promise of a cease-fire, emergency workers renewed efforts to get food and medical supplies into besieged cities and get traumatized civilians out.

Aid agencies say humanitarian help is most urgently needed in Mariupol, where residents are running out of food, water and power.

Russian warplanes were targeting convoy routes on Thursday, said Petro Andrushenko, an adviser to Mariupol’s mayor.

“Airstrikes started from the early morning. Airstrike after airstrike. All the historic center is under bombardment,” he said. “They want to absolutely delete our city, delete our people. They want to stop any evacuation.”

The capture of Mariupol would allow Russia to link up pro-Moscow enclaves in the east and the Russian-annexed Crimea to the southwest.

Ukrainian President Volodymyr Zelenskyy has urged the West to take a more active role.

Zelenskyy told Russian leaders that the invasion will backfire on them as their economy is strangled. Western sanctions have already dealt a severe blow to the economy, causing the ruble to plunge, foreign businesses to flee — including, on Thursday, investment bank Goldman Sachs — and prices to rise sharply.

“You will definitely be prosecuted for complicity in war crimes,” Zelenskyy said in a video address. “And then, it will definitely happen, you will be hated by Russian citizens — everyone whom you have been deceiving constantly, daily, for many years in a row, when they feel the consequences of your lies in their wallets, in their shrinking possibilities, in the stolen future of Russian children.”

Russian President Vladimir Putin dismissed such talk, saying the country has endured sanctions before.

The Associated Press and Reuters contributed to this report.