Russia summons UK ambassador over spy rift

Russia's Foreign Ministry has summoned the British ambassador for talks in the dispute over a nerve agent attack on a former spy in the UK.

Russia is expected to announce the expulsion of a number of British diplomats in a retaliatory measure.

Prime Minister Theresa May earlier ordered 23 Russian diplomats expelled as part of measures to punish Russia over the March 4 poisoning of former spy Sergei Skripal and his daughter Yulia in the city of Salisbury.

British Ambassador Laurie Bristow is expected at the Russian Foreign Ministry later on Saturday morning.

British Foreign Secretary Boris Johnson has accused Russian President Vladimir Putin of personally ordering the poisoning.

Mr Putin's spokesman denounced the claim.