Russian and Ukrainian officials met on the Belarusian border to discuss a ceasefire on Monday (local time) while invading Russian forces met with determined resistance from Ukrainian troops and civilians on a fifth day of conflict.
Russia faced deepening isolation and economic turmoil as Western nations, united in condemnation of its assault, hit it with an array of sanctions.
But Russian leader Vladimir Putin did not appear ready yet to think again about the invasion he unleashed on Russia's western neighbour last Thursday, having dismissed the West as an "Empire of Lies" and put his nuclear-armed units on high alert.
In the northeastern city of Kharkiv, Ukraine's second largest, Russian forces fired on residential areas on Monday, killing dozens and wounding hundreds of people, the Ukraine military said.
Video posted by the military showed thick plumes of smoke rising from apartment blocks and flashes of flames, apparently from missiles impacting. Reuters could not independently confirm the accounts.
Fighting took place throughout the night around the Ukrainian port city of Mariupol, the head of the Donetsk regional administration, Pavlo Kyrylenko, said. He did not say whether Russian forces had gained or lost ground.
Russian forces seized two small cities in southeastern Ukraine and the area around a nuclear power plant, the Interfax news agency said.
But they ran into stiff resistance elsewhere as the biggest assault on a European state since World War Two failed to make as much ground in its early days as some had expected.
The capital Kyiv was still held by the Ukrainian government, with President Volodymyr Zelenskiy, dressed in military gear, encouraged his people with a series of defiant messages.
Blasts were heard in the city before dawn and Ukrainians set up checkpoints and blocked streets with piles of sandbags and tyres as they waited to take on Russian soldiers.
In the basement of Ohmadyt Children's Hospital in Kyiv, mothers and babies huddled on makeshift beds and blankets laid out on either side of the concrete aisle.
On the streets, signboards normally used for traffic alerts showed the message: "Putin lost the war. The whole world is with Ukraine".
The talks between the two sides began with the aim of an immediate ceasefire and the withdrawal of Russian forces, the Ukrainian president's office said. The Kremlin has declined to comment on Moscow's aim.
They are being held on the border with strong Russian ally Belarus, which is a launch pad for the invading Russian troops.
"Dear friends, the President of Belarus has asked me to welcome you & facilitate your work as much as possible. Belarusian Foreign Minister Vladimir Makei said at the start. "You can feel completely secure."
The Russian delegates wore formal suits while the Ukrainians had on plain dark clothes and, in one case, a baseball cap.
Russia calls its actions in Ukraine a "special operation" that it says is not designed to occupy territory but to destroy its southern neighbour's military capabilities and capture what it regards as dangerous nationalists.
The Western-led response has been emphatic, with sanctions that effectively cut off Moscow's major financial institutions from Western markets. Russia's rouble currency plunged 30 percent against the dollar on Monday. Countries also stepped up weapons supplies to Ukraine.
BATTLE FOR THE CITIES
The Ukrainian military said Russian forces were focusing on Chernihiv city, northeast of Kyiv, and parts of Donetsk region in the east.
The Russian defence ministry said its forces had taken over the towns of Berdyansk and Enerhodar in Ukraine's southeastern Zaporizhzhya region as well as the area around the Zaporizhzhya nuclear power plant, Interfax reported. The plant's operations continued normally, it said.
Ukraine denied the nuclear plant had fallen into Russian hands, Interfax said.
UN human rights chief Michelle Bachelet said at least 102 civilians in Ukraine have been killed since Thursday, with a further 304 wounded, but the real figure is feared to be "considerably higher".
More than half a million people have fled to neighbouring countries, according to the United Nations refugee agency.
Partners in the US-led NATO (North Atlantic Treaty Organization) defence alliance were providing Ukraine with air-defence missiles and anti-tank weapons, NATO chief Jens Stoltenberg said.
The Kremlin accused the European Union of hostile behaviour, saying weapons supplies to Ukraine were destabilising and proved that Russia was right in its efforts to demilitarise its neighbour.
"Throughout Russia, the vast majority of the population has friends or relatives who live in Ukraine. Naturally, everyone's hearts are aching for what is happening to these relatives," Kremlin spokesperson Dmitry Peskov said.
The Kremlin declined to comment on whether there was a risk of confrontation between Russia and NATO. Russia has demanded that NATO never admit Ukraine.
Russia's defence ministry said on Monday its nuclear missile forces and Northern and Pacific fleets had been placed on enhanced combat duty in line with orders from Putin, Interfax said.
Over the weekend, Western nations announced sanctions including blocking some Russian banks from the SWIFT international payments system.
In an emergency move, Russia's central bank raised its key interest rate to 20% from 9.5% as the rouble slid. Authorities told export-focused companies to be ready to sell foreign currency.
It also ordered brokers to block attempt by foreigners to sell Russian securities.
Corporate giants also took action in response to the sanctions, with British oil major BP BP, the biggest foreign investor in Russia, saying it would abandon its stake in state oil company Rosneft at a cost of up to $25 billion.
PROTESTS
Protests have been held around the world against the invasion, including in Russia, where almost 6,000 people have been detained at anti-war demonstrations since Thursday, the OVD-Info protest monitor said.
The U.N. Human Rights Council agreed on Monday to Ukraine's request to hold an urgent debate this week on the invasion after Kyiv's ambassador told the Geneva forum that some of Moscow's military actions "may amount to war crimes".
Zelenskiy on Monday asked the European Union to allow Ukraine to gain membership immediately.
The EU shut all Russian planes out of its airspace, as did Canada, forcing Russian airline Aeroflot to cancel all flights to European destinations until further notice.
Russia closed its airspace to Germany, France, Spain, Italy and 23 other countries, Tass news agency reported.
Ukraine's Foreign Minister Dmytro Kuleba urged the Russian people to demand Putin stop the war.
"Look what Vladimir Putin turned your country, your great country, into. He declared an invasive war against Ukraine, he sent your sons, husbands here to kill Ukrainians, capture our lands, destroy our cities. Ukrainians did not want this war, but they will fight for their land," he said in a video released on Monday from an undisclosed location.
Reuters
