Ukraine said Sunday it had agreed to talks with Russia after four days of conflict, as Russian President Vladimir Putin ordered his defence chiefs to put nuclear "deterrence forces" on alert, report AFP.
The conflict has already killed dozens of civilians, forced hundreds of thousands to flee and turned Moscow into a global pariah.
President Volodymyr Zelensky's office said a Ukrainian delegation would meet the Russian one at the border with Belarus, which has allowed Russian troops passage to attack Ukraine.
The meeting is set to take place near Chernobyl -- the site of the world's worst nuclear disaster.
"The politicians agreed that the Ukrainian delegation would meet the Russian one without preconditions," Zelensky's office said in a statement after the president spoke to his Belarusian counterpart Alexander Lukashenko.
Ukrainian forces earlier said they had fought off a Russian incursion into Ukraine's second biggest city, Kharkiv, on day four of Russia's invasion.
As Western countries lined up to send arms into Ukraine and impose ever more stringent sanctions, Putin ordered his defence chiefs to put the country's nuclear "deterrence forces" on high alert.
Putin accused Western countries of taking "unfriendly" steps against his country.
Ukraine has reported 198 civilian deaths, including three children, since the invasion began. The UN has put the civilian toll at 64.
"The past night in Ukraine was brutal," Zelensky said. "They fight against everyone. They fight against all living things -- against kindergartens, against residential buildings and even against ambulances."
