Russian and Ukrainian forces exchanged artillery fire at the front line in Ukraine after Moscow said it had begun a truce that was firmly rejected by Kyiv.

President Vladimir Putin ordered the 36-hour ceasefire from midday on Friday to observe Russian Orthodox Christmas. Ukraine has said it has no intention to stop fighting, rejecting the purported truce as a stunt by Moscow to buy time to reinforce troops that have taken heavy losses this week.

"What ceasefire? Can you hear?" said a Ukrainian soldier, using the pseudonym Vyshnya, as an explosion rang out in the distance at the front line near Kreminna in eastern Ukraine. 

"What do they want to achieve if they keep on shooting? We know, we have learnt not to trust them."

Hours before the ceasefire was due to start on Friday Russian artillery hit a fire station in Kherson, killing one fireman.

Sporadic shelling also continued across the eastern Donbas region after midday.