Russia and Ukraine failed to make a breakthrough Thursday in their first top-level talks since Moscow's invasion two weeks ago, as Russian forces advanced on Kyiv and faced new accusations they attacked a humanitarian corridor into Mariupol.
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.
Moscow's military advances have sparked fears the capital Kyiv could soon be surrounded. Russian forces were encircling at least four major Ukrainian cities Thursday and armored vehicles rolled up to 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 Thursday, with Ukrainian President Volodymyr Zelensky accusing Moscow of launching a "tank attack" targeting a humanitarian corridor where he had dispatched a convoy 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 that attack a Russian "war crime," a position backed by top Western officials.
The White House slammed the "barbaric" use of force against civilians, while European Union foreign policy chief Joseph Borrell echoed Zelensky in calling the hospital attack a "heinous war crime."
The Russian army claimed the hospital bombing was a "staged provocation" by Ukraine.
Around 100,000 people have been evacuated in two days, Ukraine's government said Thursday.
They managed to leave areas around the northeastern city of Sumy, sites northwest of Kyiv and the eastern city of Izyum.
Moscow said it would also open daily humanitarian corridors to evacuate civilians to Russian territory, but Kyiv has insisted no evacuation routes should lead to Russia.
The UN Refugee Agency estimates more than 2.3 million refugees have left Ukraine since Russia shocked the world by invading its pro-Western neighbor on Feb. 24, and some 1.9 million Ukrainians have been internally displaced.
Overall, at least 71 children have been killed and more than 100 wounded in Ukraine since the war began, said Lyudmyla Denisova, the Ukraine parliament's point person on human rights.
The situation in Mariupol is particularly dire, with 10 days of constant attacks having left more than 1,200 civilians dead, according to the mayor.
The UN said in addition to Mariupol, 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 defense 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, claimed Moscow's operations have been purely defensive.
Asked by a Turkish reporter if Moscow was planning to attack other nations, Lavrov replied "we don't plan to attack other countries," claiming Russia "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 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 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 adviser.
The conflict has raised fears of a nuclear accident in a country with two major plants now under Russian control: Chernobyl, location of the world's worst nuclear disaster, in 1986, and Zaporizhzhia, Europe's largest nuclear plant.
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
With global anger surging online as the war rages, Facebook said late Thursday it has temporarily eased its rules regarding violent speech to allow statements like "death to Russian invaders," but not credible threats against Russian civilians.
Washington has strongly backed Ukraine, leading the push for tough international sanctions and sending weapons and other aid. A $14 billion Ukraine assistance package is making its way through Congress.
But the U.S. has ruled out enforcing a no-fly zone, and rejected a Polish plan to transfer fighter jets to Ukraine via a U.S. 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, however, 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 U.K. assets freeze and travel ban.