Russia and Ukraine failed to make a breakthrough Thursday in their first top-level talks since Moscow's invasion two weeks ago, as Russian advances sparked fears the Ukrainian capital Kyiv could soon be encircled.
After talks with Russian counterpart Sergei Lavrov in Turkey, Ukraine's Foreign Minister Dmytro Kuleba said there had been "no progress", even on a 24-hour ceasefire, although Lavrov said Moscow would keep talking.
Russian forces were encircling at least four major cities in Ukraine on Thursday, with armoured vehicles rolling up to capital Kyiv's northeastern edge, where suburbs including Irpin and Bucha have endured days of heavy bombardment.
Kyiv mayor Vitali Klitschko said half the population had fled, adding that the city "has been transformed into a fortress. Every street, every building, every checkpoint has been fortified."
The besieged southern port city of Mariupol meanwhile came under fresh assault, with Ukrainian president Zelensky accusing Moscow of launching a "tank attack" targeting a humanitarian corridor being used to try to get food, water and medicine into the city.
The attack, which Zelensky described in a video statement as "outright terror," came a day after the bombing of a children's hospital there that local officials said killed three people, including a young girl.
Zelensky branded the hospital attack a Russian "war crime", a position backed by top European Union officials.
The Russian army however claimed the hospital bombing was a "staged provocation" by Ukraine.
US Treasury Secretary Janet Yellen said the "intensifying" targeting of civilians could see Washington and its European allies step up already unprecedented sanctions on Moscow.
And the White House slammed the "barbaric" use of force against civilians, while EU foreign policy chief Joseph Borrell echoed Zelensky in calling the hospital attack a "heinous war crime".
Around 100,000 people have been evacuated in two days, the Ukrainian government said Thursday. They managed to leave areas around the northeastern city of Sumy, places northwest of Kyiv, and the eastern city of Izyum.
Moscow said Thursday it would also open daily humanitarian corridors to evacuate civilians to Russian territory, but Kyiv has insisted no evacuation routes should lead to Russia.
- 'Apocalyptic' -
The UN Refugee Agency estimates more than 2.3 million refugees have left Ukraine since Russia shocked the world by invading its pro-Western neighbour on February 24, and some 1.9 million Ukrainians have been internally displaced.
Overall, at least 71 children have been killed in Ukraine since the start of the war, and more than 100 have been wounded, said Lyudmyla Denisova, the Ukraine parliament's point person on human rights.
The situation in Mariupol is particularly dire, with ten days of constant attacks having left more than 1,200 civilians dead, according to the mayor.
Zelensky shared footage Wednesday of massive destruction at the hospital, saying the "direct strike by Russian troops" had left children under the rubble.
The UN said two other Ukrainian maternity hospitals had been attacked and destroyed, including one in Zhytomyr west of Kyiv.
Mariupol's city council reported new Russian air attacks Thursday on residential buildings, and aid agencies say it faces an "apocalyptic" situation, with no water, power or heat for more than a week.
The International Committee of the Red Cross said some residents had started fighting for food, and many had run out of drinking water.
While the hospital attack triggered global outrage, Russian defence ministry spokesman Igor Konashenkov said there were no Russian air strikes in the area, and described the incident as a "staged provocation" to stoke anti-Russian sentiment.
Lavrov, at the Turkey talks, went so far as to claim Moscow's operations have been purely defensive.
Asked by a Turkish reporter if Russia was planning to attack other nations, Lavrov replied "we don't plan to attack other countries" and claimed "we did not attack Ukraine".
He said Russian President Vladimir Putin launched the operation as the situation in Ukraine "posed a direct threat to the Russian Federation".
- 'Nowhere to run' -
On Kyiv's northeastern edge, Ukrainian soldiers described a night of fierce fighting for control of the main highway leading into the capital.
An AFP team witnessed missile strikes in Velyka Dymerka just outside Kyiv's city limits.
Ukrainian forces only had a minimal presence in the village, which locals said witnessed heavy battles overnight.
"It's frightening, but what can you do?" said Vasyl Popov, a 38-year-old advertising salesman. "There is nowhere to really run or hide. We live here."
Across Ukraine, the invasion has so far destroyed about $100 billion in roads, bridges and businesses, said Oleg Ustenko, Zelensky's chief economic advisor.
The conflict has raised fears of a nuclear accident in a country with two major plants -- Chernobyl, location of the world's worst nuclear disaster, in 1986, and Zaporizhzhia, Europe's largest nuclear plant -- now under Russian control.
The UN's atomic watchdog IAEA warned of a "dire" situation, with power out at the Chernobyl plant and all communications with Ukraine there severed.
But after separate talks in Turkey Thursday with Russian and Ukrainian officials, the IAEA said Moscow and Kyiv were "ready to work" with the agency to ensure nuclear safety.
- Chelsea owner targeted -
Washington has strongly backed Ukraine, leading the push for tough international sanctions and sending weapons and other aid. A $14 billion Ukraine aid package is making its way through Congress.
But the US has ruled out enforcing a no-fly zone, and rejected a Polish plan to transfer fighter jets to Ukraine via a US air base for fear of being drawn directly into the conflict.
State Department spokesman Ned Price said ground-based defense systems have proven effective against Russia's "formidable" air force.
"We will continue to provide our Ukrainian partners with the surface-to-air systems that they need to take on the threat that they face from Russian missiles, from Russian rockets, from artillery," he said Thursday.
Lavrov though warned the supply of deadly weapons to Ukraine was "creating a colossal danger" for countries providing them.
Western sanctions have targeted Russia's financial system and its oligarchs, including Chelsea football club owner Roman Abramovich, who was hit Thursday by a UK assets freeze and travel ban.
This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.
