Prime Minister Rishi Sunak is expected to stay in close contact with Western allies about the extraordinary events in Russia, where a rebellion against Vladimir Putin appeared to be defused when mercenaries turned back from Moscow and their chief was ordered to Belarus.
Wagner boss Yevgeny Prigozhin will leave Russia as part of a deal to end his uprising and charges against him will be dropped, the Kremlin said.
Russian authorities will not prosecute troops who joined him in the mutiny and will offer Russian military contracts to those who did not.
Mr Prigozhin told his forces to halt their advance on the capital to avoid “bloodshed” as part of the deal, which de-escalated a growing crisis that amounted to the greatest ever security challenge to the Russian president.
The sudden retreat came at the end of a dramatic day during which the rebel leader vowed to topple Moscow’s military leadership, seized a southern Russian city and sent a convoy towards the capital.
The agreement averting a descent into civil war was mediated by the Belarusian president Alexander Lukashenko, who said he had his close ally Mr Putin’s approval.
Earlier, as the mercenaries headed towards Moscow and authorities prepared defences, Mr Sunak held talks with fellow leaders about what UK defence officials described as “the most significant challenge” to the Kremlin in recent times.
The Prime Minister spoke to US president Joe Biden, French president Emmanuel Macron and German chancellor Olaf Scholz on Saturday afternoon “to discuss the situation in Russia and reiterate their continuing support for Ukrainian sovereignty”, Downing Street said.
“The leaders have agreed to stay in close contact in the coming days,” a No 10 spokesperson said.
It followed a meeting of the Government’s emergency Cobra committee chaired by Foreign Secretary James Cleverly, who also joined a call with fellow G7 foreign ministers to discuss the fast-moving situation.
The Prime Minister urged all parties involved in the Russian infighting to protect civilian lives.
“We’re keeping a close eye on the situation, as it’s evolving on the ground as we speak,” Mr Sunak told the BBC.
“The most important thing I’d say is for all parties to be responsible and to protect civilians, and that’s about as much as I can say at this moment.”
Pressed on advice for British nationals remaining in Russia, Mr Sunak said the UK has “had long-standing travel advice against travel to Russia” and “people should keep checking the Foreign Office website for updates”.
Mr Cleverly tweeted that “we are monitoring the situation carefully and liaising closely with our allies” and “we continue to urge British citizens to follow FCDO (Foreign, Commonwealth and Development Office) travel advice”.
An FCDO spokesperson said: “The Foreign Secretary has chaired a meeting of COBR to update on the latest situation, particularly with respect to British nationals in Russia.”
In the morning, the Ministry of Defence (MoD) said that “over the coming hours, the loyalty of Russia’s security forces… will be key to how the crisis plays out” as Wagner forces moved towards the Russian capital.
In its daily intelligence briefing, the department said the feud between the Wagner group and the Russian defence ministry “escalated into outright military confrontation” in the early hours of Saturday.
“In an operation characterised by Prigozhin as a ‘march for freedom’, Wagner Group forces crossed from occupied Ukraine into Russia in at least two locations,” the MoD said.
It said that in the city of Rostov-on-Don near the Ukrainian border, “Wagner has almost certainly occupied key security sites”, including the Russian military headquarters that oversees the fighting in Ukraine.
Units were “almost certainly aiming to get to Moscow”, according to the MoD.
“Over the coming hours, the loyalty of Russia’s security forces, and especially the Russian National Guard, will be key to how the crisis plays out.
“This represents the most significant challenge to the Russian state in recent times.”
Mr Putin called the rebellion a “betrayal” in a televised address but Mr Prigozhin denied the claim and called his fighters “patriots”.
Before their retreat, the mercenaries had moved north towards Moscow throughout the day, with the governor of Lipetsk province, around 225 miles south of the capital, confirming they were crossing the region.
Wagner troops have been fighting alongside Russian soldiers in Ukraine and succeeded in taking the eastern city of Bakhmut, where the bloodiest and longest battles have raged.
But Mr Prigozhin recently stepped up his criticism of Russia’s military leadership, accusing it of botching the war and shelling his fighters.
The rebellion was expected to further hamper Moscow’s war effort as the early stages of a Ukrainian counter-offensive unfold.
Ukrainian president Volodomyr Zelensky said Moscow was suffering “full-scale weakness”.
