Russian forces neared Kyiv on Thursday, as international leaders and Ukraine accused Russia of a "barbaric" attack on a children's hospital in the besieged city of Mariupol.
As the violence continues, Russia and Ukraine's foreign ministers are in Turkey for the highest-level talks of the conflict so far, though hopes for a breakthrough remain low.
Ukraine's President Volodymyr Zelensky said 35,000 civilians had managed to flee cities under Russian attack on Wednesday, but there was little relief in Mariupol where the mayor said relentless bombardment had killed over 1,200 civilians in the nine-day siege.
And there were fears that the capital could soon be encircled as well, with Russian tanks just a few kilometres (miles) from the city limits in some places.
Zelensky shared video footage showing massive destruction at the recently refurbished hospital in the southern port city of Mariupol, condemning the attack as a "war crime."
A local official said the attack wounded at least 17 staff, though no deaths were immediately reported. Zelensky said the "direct strike by Russian troops" had left children under the wreckage.
Russia's foreign ministry did not deny the attack but accused Ukrainian "nationalist battalions" of using the hospital to set up firing positions after moving out staff and patients.
Video shared from the site by rescue workers showed a scene of complete devastation, with the wounded being evacuated, some on stretchers, past charred and burning carcasses of cars and a massive crater by the building.
Inside, debris, shattered glass and splintered wood littered corridors, administrative offices and bedrooms, with mattresses thrown from their frames.
The White House slammed the "barbaric" use of force against civilians, while British Prime Minister Boris Johnson called the attack "depraved."
And there was no let-up in the violence overnight, with officials in Sumy in the northeast reporting two women and a 13-year-old boy were killed in bombing in the Velyka Pysarivka region.
He said a petrol depot and a residential area had also been hit in the area where heavy fighting has been taking place.
The Ukrainian General Staff meanwhile said Russian forces were continuing their "offensive operation" to encircle Kyiv, while pressing attacks on a string of other cities across the country.
At a deserted service station on a motorway northeast of the city, a Ukrainian officer warned vehicles not to go any further on Wednesday.
"The Russian tanks are just over there, two kilometres away," he told one car, ordering it to turn round and go back.
"Drive in a zig-zag to avoid their shots," he advised.
In Turkey meanwhile, Russian Foreign Minister Sergei Lavrov and his Ukrainian counterpart Dmytro Kuleba are due to meet later in the first high-level talks since the conflict began.
But Kuleba has already warned his expectations are "limited."
So far, the parties have been engaged in lower-level talks in Belarus, largely over humanitarian issues and involving Ukrainian officials but no Russian ministers.
Those discussions have produced several attempts to get civilians out of cities under attack, many of which have failed after so-called humanitarian corridors came under attack.
On Wednesday, at least 35,000 civilians were able to leave the cities of Sumy, Enerhodar and areas around Kyiv, Zelensky said.
He said he hoped the evacuations would continue on Thursday with three more routes set to open out of Mariupol, Volnovakha in the southeast and Izium in eastern Ukraine.
Previous attempts to allow civilians to leave Mariupol in particular have collapsed, with aid groups warning of a catastrophic situation in the city where basic services have halted.
Russia's war has sent around 2.2 million refugees across Ukraine's borders in what the United Nations has called Europe's fastest-growing refugee crisis since World War II.
The conflict has raised fears of a nuclear accident in a country with major nuclear plants and the site of the Chernobyl disaster.
The UN's atomic watchdog said Wednesday it saw "no critical impact on safety" at Chernobyl, location of the world's worst nuclear disaster in 1986, despite a loss of power there.
But it warned it was not receiving updates from either Chernobyl or Zaporizhzhia, Europe's largest nuclear plant, which is also now under Russian control.
The United States meanwhile rejected Russian claims that it was involved in bioweapons research in Ukraine, and warned Russia could be preparing to use chemical or biological weapons in the war.
Washington has strongly backed Ukraine, leading the push for tough international sanctions and sending weapons and other aid.
But it has ruled out enforcing a no-fly zone and rejected a Polish plan to transfer fighter jets via a US air base for fear of being drawn into the conflict directly.
Washington has however beefed up defences in Poland, where it said Wednesday it was sending two new surface-to-air missile batteries.
And Britain said it was preparing to send more portable missile systems to help Ukraine, in addition to more than 3,000 anti-tank weapons sent so far, while Canada pledged an additional US$50 million worth of military equipment.
The US House of Representatives meanwhile green-lit a spending package including nearly US$14 billion for Ukraine and allies in eastern Europe. It will now need to be rubber-stamped by the Senate.
The International Monetary Fund has also approved a US$1.4-billion emergency package for Kyiv to provide "critical financial support."
Western nations and allies are also trying to squeeze Moscow with unprecedented sanctions.
British Foreign Secretary Liz Truss on Wednesday urged the entire G7 to ban Russian oil imports, saying the world's top economies should "go further and faster" in punishing Moscow for invading Ukraine.
But some nations are wary, with French Economy Minister Bruno Le Maire warning the current spike in energy prices could produce effects comparable to the 1973 oil shock.