LONDON, March 5. /TASS/. The Russian embassy should probably host an open house day for British intelligence agencies, the embassy said in an ironic tweet, commenting on an article in The Guardian.

The newspaper said earlier that "intelligence services investigated unusual activity at the Russian embassy in London in the days before and after the novichok poisoning."

According to the Guardian, "MI5, MI6 and GCHQ [Government Communications Headquarters] looked into unprecedented ‘frantic comings and goings’ at the building in Kensington in the days leading up to the poisoning of the former Russian spy Sergei Skripal and his daughter Yulia, a source with knowledge of the investigation told the Press Association."

"The intelligence agencies have been investigating unusual and increased activity at the Russian embassy in Kensington in the days leading up to and after the attack on the Skripals," the newspaper quoted the source as saying. "As would be expected, the UK security services have eyes on known and undeclared foreign intelligence operatives," the source added.

Skripal saga

According to London, former Russian military intelligence (GRU) Colonel Sergei Skripal, 66, who had been convicted in Russia of spying for Great Britain and later swapped for Russian intelligence officers, and his daughter Yulia, 33, suffered the effects of an alleged nerve agent in the British city of Salisbury on March 4, 2018. Claiming that the substance used in the attack had been a Novichok-class nerve agent developed in the Soviet Union, London rushed to accuse Russia of being involved in the incident. Moscow rejected all of the United Kingdom’s accusations, saying that neither the Soviet Union nor Russia ever had any program aimed at developing such a substance.

Chief Executive of the Defense Science and Technology Laboratory (DSTL) at Porton Down Gary Aitkenhead said later that British experts had been unable to identify the origin of the nerve agent used in the attack on the Skripals.