Update by BBC
The chief of the Wagner mercenary force has called for a rebellion against the Russian army – although he has denied attempting a coup.
Wagner says it has taken the Russian city of Rostov-on-Don near the Ukraine border – residents have been told to stay indoors.
BBC News Russian sources also say Wagner mercenaries have seized military facilities in Voronezh, which is halfway between Rostov and Moscow
As mercenaries move towards Moscow, the mayor of the capital city has told residents to avoid travelling
President Putin decries “betrayal” and “treason” in a TV speech, promising to punish rebels.
On Friday night, security in Russia was tightened, the internet was restricted and military trucks were spotted on Moscow streets.