The Kremlin on Monday accused US President Joe Biden of escalating the war in Ukraine over reports that he has allowed Kyiv to use long-range missiles supplied by Washington to strike targets inside Russia.

The comments from Moscow came as Ukraine said a fresh Russian strike on the Black Sea port city of Odesa had killed at least eight people and wounded 18, following a massive weekend attack on the country's creaking energy infrastructure.

Ukraine has long sought authorisation from Washington to use the powerful Army Tactical Missile System, known by its initials as ATACMS, to hit military installations – and in particular airfields – inside Russia.

Ukraine says it is mainly seeking to use the weapons to prevent Russian aerial bombardments that have levelled entire districts and towns near the front line and decimated energy facilities across the country.

A US official spoke about the policy shift on condition of anonymity on Sunday, saying the decision had come in response to Russia's deployment of thousands of North Korean troops to aid its war effort.

"It's obvious that the outgoing administration in Washington intends to take steps in order to continue fuelling the fire and provoke a further escalation of tensions," Kremlin spokesman Dmitry Peskov told reporters in Moscow.

"If such a decision was really formulated and announced to the Kyiv regime, then of course it's a qualitatively new spiral of tensions and a qualitatively new situation from the point of view of the US's engagement in the conflict," Peskov added.

He said President Vladimir Putin had expressed Russia's position clearly in September when the leader said that such a move would put Nato "at war" with Russia.

Putin said in September that if Ukraine were to attack Russia with the long-range missiles then Moscow would "take the appropriate decisions based on the threats". (AFP)