Russian forces attacked Ukrainian cities with artillery and cruise missiles on Saturday but President Volodymyr Zelenskyy said capital Kyiv remained in their hands.

Russia's invasion force had been slowed by stiff resistance from Ukrainian troops, keeping them outside Kyiv, a senior US defence official has said, according to news agency AFP.

Earlier, head of Ukrainian president Volodymyr Zelenskiy's office, Mikhail Podolyak said it was untrue that Ukraine has refused negotiations with Russia and added that Moscow set out “unacceptable conditions and ultimatum demands”.

On Saturday, Vladimir Putin's press secretary Dmitry Peskov said Putin ordered a halt to the Russian advance after offering negotiations, but since Ukraine refused them, the assault was resumed.

“Ukraine, of course, did not refuse negotiations.

"But precisely...which, by the way, have not happened yet. Ukraine and President Zelensky categorically renounces any unacceptable conditions or ultimatum demands from the Russian side,” Podolyak had said.

Meanwhile. Germany and its Western allies have agreed to cut Russia out of the SWIFT global payment system, a spokesperson for the German government said.

Ukrainian Health Minister Viktor Lyashko Saturday said 198 civilians, including three children, had been killed in the conflict and 1,115 wounded.

Around 3,500 Russian soldiers have been killed or injured so far, an adviser to Ukrainian President Volodymyr Zelenskiy said.