Russian forces have bombarded scores of towns in Ukraine on Christmas Day as President Vladimir Putin says he is open to negotiations – a stance Washington has dismissed as posturing.

Russia on Sunday launched more than 10 rocket attacks on the Kupiansk district in the Kharkiv region, shelled more than 25 towns along the Kupiansk-Lyman frontline and hit almost 20 towns in Zaporizhzhia, Ukraine’s top military command said.

Mr Putin’s February 24 invasion of Ukraine – which Moscow calls a “special operation” – has triggered the deadliest European conflict since World War II and the biggest confrontation between Moscow and the West since the 1962 Cuban Missile Crisis.

Despite Mr Putin’s latest offer to negotiate, there is no end in sight to the 10-month conflict.

“We are ready to negotiate with everyone involved about acceptable solutions but that is up to them – we are not the ones refusing to negotiate, they are,” Mr Putin told Rossiya 1 state television in an interview broadcast on Sunday.

An adviser to Ukrainian President Volodymyr Zelensky said Mr Putin needed to return to reality and acknowledge it was Russia that did not want talks.

“Russia single-handedly attacked Ukraine and is killing citizens,” the adviser, Mykhailo Podolyak, tweeted.

“Russia doesn’t want negotiations but tries to avoid responsibility.”

Russian attacks on power stations have left millions without electricity and Mr Zelensky said Moscow would aim to make the final few days of 2022 dark and difficult.

“Russia has lost everything it could this year,” he said in an evening video address on Christmas Day.

“I know darkness will not prevent us from leading the occupiers to new defeats but we have to be ready for any scenario.”

Ukraine traditionally celebrates Christmas Day on January 7, the same day as Russia, rather than December 25.

However, some Orthodox Ukrainians decided to celebrate the holiday on December 25 this year. Ukrainian officials, including Mr Zelensky and the prime minister issued Christmas wishes on Sunday.

The Kremlin says it will fight until all its territorial aims are achieved, while Kyiv says it will not rest until every Russian soldier is ejected from the country.

Asked if the geopolitical conflict with the West was approaching a dangerous level, Mr Putin on Sunday said: “I don’t think it’s so dangerous.”

Kyiv and the West say Mr Putin has no justification for what they cast as an imperial-style war of occupation.

A senior Belarusian defence ministry official said on Sunday Russian-supplied Iskander tactical missile systems, capable of carrying nuclear warheads, and S-400 air defence systems had been deployed to Belarus and prepared to perform their intended tasks.

Russian forces used Belarus as a launch pad for their abortive attack on the Ukrainian capital, Kyiv, in February, and there has been a growing flurry of Russian and Belarusian military activity in recent months.

Ukrainian and Russian media reported blasts were heard at Russia’s Engels air base near the city of Saratov on Monday, hundreds of kilometres from the Ukraine frontlines.

There was no immediate official confirmation and Reuters was not able to independently verify the reports.

Ukraine has never publicly claimed responsibility for attacks inside Russia but has said such incidents are “karma” for Russia’s invasion.

-AAP