The UK will expel 23 Russian diplomats after Moscow refused to explain how a Russian-made nerve agent was used on a former spy in Salisbury, the PM says.

Theresa May said the diplomats, who have a week to leave, were identified as "undeclared intelligence officers".

She also revoked an invitation to Russia's foreign minister, and said the Royal Family would not attend the Fifa World Cup later this year.

Russia denies being involved in the attempted murder of Sergei Skripal.

The Russian Embassy said the expulsion of 23 diplomats was "unacceptable, unjustified and short-sighted".

Former spy Mr Skripal, 66, and his daughter, Yulia Skripal, 33, remain critically ill in hospital after being found slumped on a bench on 4 March.

Det Sgt Nick Bailey also fell ill responding to the incident, and is in a serious but stable condition, but is thought to be improving.

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Video content Video caption: Theresa May statement on UK-Russian political relations Theresa May statement on UK-Russian political relations