Russia launched a "massive" attack on several Ukrainian cities overnight on Monday, President Volodymyr Zelensky has said, a day after he warned of strikes over the Christmas period.

The town of Siversk had served as a stronghold in the portion of eastern Donetsk still under Ukrainian control. Moscow wants Kyiv to surrender the town as part of a peace deal.

Volodymyr Zelensky said on Tuesday that several draft documents, including on security guarantees, had been prepared after Ukrainian officials held talks in Miami with US counterparts on ending Russia's war.

The U.S. findings have been consistent since Putin launched his full-scale invasion in 2022. They largely align with the views of European leaders and spy agencies that he covets all of Ukraine and territories of former Soviet bloc states, including members of the NATO alliance, according to the sources.

Oil futures added modestly to gains with market focus on efforts toward a Russia-Ukraine peace agreement and stepped up U.S. actions against Venezuela.

Russian President Vladimir Putin declares Russia's Ukraine war goals will be achieved through negotiations or military force as diplomatic efforts.

Ukrainian negotiators held a new round of talks on a settlement to the war with Russia with U.S. and European teams on Friday and agreed to pursue their joint efforts, top Ukrainian negotiator Rustem Umerov said.