The British government said on Thursday it had sanctioned steel manufacturing and mining company Evraz, whose biggest shareholder is sanctioned billionaire Roman Abramovich, in response to Russia's invasion of Ukraine.
"The steel manufacturing and mining company operates in sectors of strategic significance to the Government of Russia," the government said in a statement.
"Today's asset freeze means no UK citizen or company can do business with them."
The government issued a separate licence which said people could continue business operations involving Evraz's North American subsidiaries.
Britain said Evraz produces 28% of all Russian railway wheels and 97% of rail-tracks in Russia, making it of vital significance as Russia uses rail to move key military supplies and troops to the frontline in Ukraine.
Shares in Evraz have been suspended from trading since March 10, when Britain imposed sanctions on Abramovich. The firm said on March 11 that 10 members of its board had quit, leaving only the chief executive.
Abramovich owns a 28.64% stake in the company, and Evraz has previously said he does not have effective control of the company.