(Reuters) - President Vladimir Putin and Moscow Mayor Sergei Sobyanin joined other worshippers for an Easter service led by the head of Russia's Orthodox Church, Patriarch Kirill, a faithful backer of the Russian leader and an advocate for the war in Ukraine.

Hours after declaring a unilateral Easter ceasefire that Kyiv said was just words as fighting continued, Putin and Sobyanin stood in Moscow's main church, the Cathedral of Christ the Saviour, while Kirill led a procession, video of the service showed.

Holding a lit thin red candle and donning a dark suit, white shirt and a red tie as in years past, the Russian leader crossed himself several times when Kirill announced "Christ is risen."

The traditionally sung service starts late on a Saturday and lasts into the early hours of Sunday.

For Putin, the Orthodox faith is central to his world view and he always attends services during major church holidays. For Orthodox Russians, Easter is the most important religious holiday.

At the service, Krill called for "lasting and just peace can be established in the vast expanses of historical Rus," RIA state news agency reported, in what was a reference to a medieval territory that encompassed parts of what is now Ukraine, Belarus and Russia.

"How wonderfully it was said, do not do evil to another and do not treat others as you would not want them to treat you," TASS agency cited Kirill as saying.

"If people adhered to this holiday commandment, then life would be completely different: family and social life and - let me say this - inter-governmental."

Kirill has strongly backed the war in Ukraine, now in its fourth year. Thousands have been killed, the vast majority of them Ukrainians, and millions driven from their homes since Putin ordered the invasion of Ukraine in February 2022.

(Reporting and writing by Lidia Kelly in Melbourne)