British interior minister Theresa May said the government would summon Russia's ambassador to London to express its displeasure at Moscow's failure to cooperate with an investigation into the murder of ex-KGB agent Alexander Litvinenko.

May also told parliament that asset freezes would be put in place relating to the case.

Earlier on Thursday, an inquiry found Russian President Vladimir Putin probably approved the murder of Litvinenko in 2006. The Kremlin has denied any involvement in the death.