Russian forces are believed to be preparing to launch another major assault on Avdiivka, a Ukrainian stronghold in the eastern region of Donetsk.

One analyst says the move is part of a plan by President Vladimir Putin to ramp up Russia's offensive ahead of the presidential election scheduled for next March.

A US think tank, the Institute for the Study of War, said on Friday, "Russian forces are preparing for a third series of larger assaults near Avdiivka."

Yury Fedorov, who specializes in Russia's security and nuclear strategy, told NHK that Russia is trying to create the conditions needed to achieve Putin's strategic aim to occupy the whole of the Donetsk region.

He indicated that Russian forces are increasing their offensive in view of the upcoming presidential election.

Fedorov says it will not be ideal for Putin to start campaigning for the presidential election before Russia wins the war.

He said even if Russia takes Avdiivka, it will need many more troops to advance beyond that point, so Avdiivka will probably be the last town that it tries to take.

Russian forces launched massive drone attacks again on Friday, causing damage over a wide stretch of land.

Ukrainian President Volodymyr Zelenskyy said on social media, "As winter approaches, Russian terrorists will try to cause more harm. We will be fighting back."