(Reuters) - Traffic restrictions remained on the M-4 "Don" major expressway in the Moscow and Tula regions on Sunday, the Federal Road Agency said on the Telegram messaging app.

"According to earlier decisions made in the regions, the restriction of traffic along the M-4 'Don' (highway) in the Tula and Moscow regions remains in place," the agency said.

Heavily armed Russian mercenaries who had advanced most of the way to Moscow on Saturday then halted their approach, de-escalating a major challenge to President Vladimir Putin's grip on power, in a move their leader said would avoid bloodshed.

(Reporting by Lidia Kelly in Melbourne; Editing by William Mallard)