Russian officials are restricted from travelling abroad — British intelligence

This is stated in their daily report.

This is likely how the Kremlin wants to prevent escape or defection. The intelligence suggests that some of the officials were forced to "forfeit" their passports to the FSB.

"This is a widening of existing measures that date from the Soviet era. Travel restrictions were tightened after the Russian annexation of Crimea in 2014," the report said.

Intelligence adds that travel restrictions will only get tighter.