Russia will respond to Ukraine's latest attacks as and when its military sees fit, the Kremlin said on Thursday, accusing Kyiv of state terrorism and confirming that President Vladimir Putin had told Donald Trump that Moscow was obliged to retaliate.

Ukraine used drones to strike Russian heavy bomber planes at air bases in Siberia and the far north at the weekend, and Russia also accused it of blowing up rail bridges in the south of the country, killing seven people.

Kremlin spokesman Dmitry Peskov, at his daily briefing with reporters, highlighted comments made by Putin a day earlier about the railway attacks.

"The president described the Kyiv regime as a terrorist regime, because it was the regime's leadership that consciously gave the order, the command, the order to blow up a passenger train. This is nothing other than terrorism at the state level. This is an important statement by the president," said Peskov.

Russia has not yet provided evidence that Ukrainian leaders ordered the rail attacks, and Kyiv has not acknowledged responsibility.

Ukrainian attacks inside Russia and Russian air strikes and advances on the battlefield have escalated the war that began in February 2022, damaging prospects for peace talks that the two sides resumed in Turkey last month.

Peskov noted, however, that Putin had supported the view of Foreign Minister Sergei Lavrov at a meeting on Wednesday that working-level contacts with Ukraine should continue.

Peskov said Putin and Trump did not discuss holding a face-to-face meeting when they spoke on Wednesday. He said there was a general understanding that such a meeting was necessary, but it had to be properly prepared.

The two did not discuss the possible lifting of sanctions against Russia, Peskov said in reply to a question.