Russia has revoked the accreditation of six British diplomats it has accused of spying, according to Russian state media.

The country's security service FSB said it had received documents indicating Britain's involvement in inflicting "a strategic defeat" on Russia, RIA Novosti news agency reported.

The six diplomats have been named and pictured on Russian state TV. The UK Foreign Office has been approached for comment.

It comes as Prime Minister Sir Keir Starmer arrives in Washington for talks with US President Joe Biden about the war in Ukraine, including whether to give Kyiv permission to fire their missiles at targets inside Russia.

Russian President Vladimir Putin has suggested Moscow would regard this as a serious escalation of the war which equates to "direct participation" of Nato countries.

“If that is the case, we will take corresponding decisions based on the threats that will be created to us,” he said on state TV.

A statement from the FSB about the six diplomats said they had shown signs of conducting intelligence and were tasked with inflicting a "strategic defeat on our country", Russian media report.

An FSB officer told Russian media "hints" to "stop this practice [of gathering intelligence]", were not heeded.

The security service added that it would revoke accreditation from more British diplomats if they are found to be involved in similar activity.