Evacuation routes in jeopardy as Russia continues shelling near strategic Ukrainian cities

The latest:

An attempt to evacuate civilians from the bombarded port of Mariupol and deliver food, water and medicine was thrown into jeopardy Tuesday by what Ukraine said was continued shelling by Russian forces as conditions inside the strategic city of 430,000 grew more desperate.

Corpses littered the streets of Mariupol, where besieged residents have increasingly turned to breaking into stores to try to feed themselves. People got water from streams or by melting snow.

Europe's worst refugee crisis since the Second World War grew even more severe, with UN officials reporting that two million people have now fled Ukraine.

Moscow's forces have laid siege to Ukrainian cities and cut off food, water, heat and medicine in a growing humanitarian disaster. But for days, attempts to create corridors to safely evacuate civilians have stumbled amid continuing fighting and objections to the proposed routes.

One evacuation attempt Tuesday did appear at least partially successful: A convoy of buses packed with people fleeing the fighting moved along a snowy road from Sumy, a northeastern city of a quarter-million people, according to video from the Ukrainian communications agency.

The Russian military said 723 people were evacuated from Sumy to the Ukrainian city of Poltava. It identified them as mostly citizens of India, with the rest from China, Jordan and Tunisia. It made no mention of any Ukrainians among those evacuated.

Hours before the convoy reached Sumy, overnight strikes killed 21 people there, including two children, according to the Ukrainian general prosecutor's office. Since the invasion began, more than 400 civilian deaths have been recorded by the UN human rights office, which said the true number is much higher.

Meanwhile, buses emblazoned with red cross symbols carried water, medicine and food toward the encircled southern port of Mariupol, scene of some of the worst desperation. Vereshchuk said the vehicles would then ferry civilians out of the city of 430,000 people.

But soon after officials announced that buses were on their way, the Ukrainian president's office said it had been informed of shelling on the escape route.

It is unclear whether the supply convoy made it to Mariupol — and it appeared unlikely that civilians would be able to board the buses to get out.

The deputy mayor of Mariupol cast doubt on the evacuations, telling the BBC that Russian forces continued to pound areas where people were trying to gather ahead of being taken out. He said some roads were blocked, while others were mined.

"So we cannot establish sustainable ceasefire and safety route at the moment," Serhiy Orlov said. "So we still have ... a city in blockade."

The city is without water, heat, working sewage systems or phone service. Authorities planned to start digging mass graves for all the dead.