More than 2,000 civilians have been killed so far in Russia's invasion of Ukraine, the country's emergency service has said.
It came as Russian forces were closing in on the Ukrainian capital Kyiv and attacks across the country's main cities intensified seven days after the start of the invasion.
"Children, women and defence forces are losing their lives every hour," the Ukrainian emergency service said.
Ukrainian President Volodymyr Zelenskky expressed outrage after a Russian strike targeting a TV tower in Kyiv also caused damage to the nearby site of the Babi Yar Holocaust memorial.
Russia has also renewed its assault on Ukraine's second-largest city, Kharkiv, in a pounding that lit up the skyline with balls of fire above populated areas.
It comes as Russia expects to discuss a ceasefire with Ukraine during the next round of peace talks in Belarus on Thursday morning, Russian news agencies citing Moscow's negotiator Vladimir Medinsky have reported.
What's Happening In Kyiv?
Kyiv's mayor said Russia is gathering forces "closer and closer" to the Ukrainian capital after a long convoy of military vehicles stalled around 20 miles northwest of the city in the early hours of Wednesday.
Ukraine said it destroyed two Russian planes in an airborne battle over the capital.
Ukraine's air force said Ukrainian MIG-29 fighters fought two Russian planes in a battle over the region, destroying two planes and losing one fighter of their own.
Following damage to the Holocaust memorial in the capital, Mr Zelenskyy expressed concern that other historically significant and religious sites could be targeted and called on Jews around the world to protest the invasion.
"This is beyond humanity," Mr Zelensky, who is Jewish, said in a speech posted on Facebook. "They have orders to erase our history, our country and all of us."
Russia's defence ministry has urged Kyiv residents to flee, saying it would strike unspecified areas used by Ukraine's security services and communications.
But with a large convoy of Russian armoured vehicles approaching, a defiant mayor Vitali Klitschko said: "We are preparing and will defend Kyiv! Kyiv stands and will stand."
What's The Situation In Other Key Cities?
Russian troops have responded by shelling Kharkiv with heavy rocket launchers and air attacks after their advance on the city was stopped, a Ukrainian official has said.
"Kharkiv today is the Stalingrad of the 21st century," said Oleksiy Arestovich, an adviser to Ukraine President Volodymyr Zelenskyy.
Oleg Sinehubov, head of the Kharkiv regional administration, said that over the past 24 hours 21 people were killed and at least 112 were injured by Russians over the past 24 hours.
Explosions have thundered on Constitution Square, near the buildings of the City Council and the Palace of Labor, on Wednesday.
A missile attack also destroyed the building of the regional police department in Kharkiv and the university building, which is located across the street.
Kharkiv, the country's second-largest city, has suffered some of the worst attacks from the air, including a paratrooper assault on a military hospital overnight.
Mr Arestovich said that several Russian planes have been shot down over Kharkiv.
Meanwhile, Russia claims to have seized the southern city of Kherson after taking the railway station and port overnight, although local authorities say it's still under their control.
If the Russian claim is true, it would be the largest city in Ukraine to fall so far.
Fighting is also escalating in the southeastern city of Mariupol, with its mayor saying Russian forces are "actively preventing the evacuation of citizens".
Elsewhere, at least four people, including a child, have been killed after homes were hit by a missile strike in the northwest city of Zhytomyr.
Russian President Vladimir Putin's forces are also attempting to keep Sumy, Lebedyn and Okhytrka surrounded, according to Ukrainian military sources.
And Russia also reportedly has naval forces in the Black Sea preparing a landing - and has cut off Ukrainian access to the Sea of Azov.
Are More Talks Planned - And How Is The West Responding?
The escalation of attacks on crowded cities followed an initial round of talks between outgunned Ukraine and nuclear power Russia on Monday that resulted in only a promise to meet again.
Russian news agencies are now reporting that the next round of peace talks will take place in Belarus on Thursday, with a ceasefire set to be discussed between the two sides.
The Russian army is providing a security corridor for the Ukrainian delegation, TASS has reported.
Mr Zelenskky had said earlier Russia must stop bombing before another meeting.
In an interview with CNN on Tuesday, Mr Zelenskyy condemned Russia for indiscriminately attacking Ukrainian citizens and historical landmarks.
He said: "As you can see, no one is being very careful about the targets. We see the children are being killed... We are defending our right to life."
The president has maintained a dialogue with Western leaders, including UK Prime Minister Boris Johnson and European Council President Charles Michel.
Mr Zelenskyy tweeted to say he has "coordinated actions" with Mr Johnson, while he was awaiting "positive signals" about Ukraine's bid for EU membership after talking to Mr Michel.
Elsewhere, US President Joe Biden said the Russian president must "pay a price" for his invasion of Ukraine as he announced the closure of US airspace to Russian flights.
At Least 800,000 Flee Ukraine Amid Fears Of Violence Escalating
Russia's unrestrained bombing actions on Tuesday raised concerns that more civilians could be killed in strikes.
Around 874,000 people have fled Ukraine, and the UN refugee agency has warned the number could surpass the one million mark soon.
It comes as Russian forces continue their heavy shelling of cities like Mariupol - and fears that the invaders will be increasingly indiscriminate with their attacks in the face of Ukrainian opposition.
The country's defence forces added that Russian troops were stopped in Kozelets, Bobrovytsia and Makiiv, while Moscow reportedly "lost their offensive potential" in parts of Svitilnya, Peremoha and Hostroluchcha.
Ukrainian officials believe that Belarus is preparing to join Russia in the fighting, with satellite imagery showing Belarusian aircraft assembling near the border.