British government security ministers are holding an emergency meeting to discuss the investigation into the poisoning in England of a Russian who spied for Britain.

The meeting Home Secretary Amber Rudd is leading on Saturday will cover the latest police and intelligence reports from Salisbury, where a military-supported investigation is underway.

Police are looking for clues to the mysterious attack on former Russian military intelligence officer Sergei Skripal and his daughter, Yulia.

They were found unconscious on a bench near the River Avon in Salisbury on Sunday. They remain in critical condition in a local hospital, poisoned with what authorities say is a rare nerve agent

Police are searching for clues at the gravesite of Skripal's son and at Skripal's house. A restaurant and pub have also been searched.