Patriarch Kirill, head of Russia's Orthodox Church, down with severe Covid symptoms

The head of the Russian Orthodox Church, 75-year-old Patriarch Kirill, has Covid and will self isolate, his church said in a statement Friday.

"All planned meetings and trips in the coming days of His Holiness Patriarch Kirill are cancelled," it said, adding that he needed "bed rest and isolation."

The patriarch was absent from a grand Kremlin ceremony later on Friday in which Russia announces the annexation of four occupied Ukrainian regions.

A leader of the Russian Orthodox Church since 2009, Patriarch Kirill is a staunch supporter of President Vladimir Putin's policies.

After Putin announced a mobilisation last week, triggering protests and an exodus of men, the patriarch suggested that Russian soldiers dying in Ukraine would go to heaven.

"It someone, driven by a sense of duty and the need to fulfil an oath, remains true to his calling and dies in the line of military duty then he undoubtedly commits an act of tantamount sacrifice," he said at a sermon last Sunday.

"We believe this sacrifice washes away all the sins that a person has committed."

The UK and Canada have placed sanctions on Patriarch Kirill for his backing of the what the Kremlin calls its "special military operation" in Ukraine.