UK threatens Russia with cyber attack - report

Britain would consider launching a cyber attack against Russia in retaliation if Russia targeted British national infrastructure, the Sunday Times reports.

Britain's relations with Russia are at a historic low, after it blamed Russia for a nerve agent attack on former Russian spy Sergei Skripal and his daughter in England, prompting mass expulsions of diplomats.

Russia has denied involvement, and on Saturday also condemned strikes against Syria by Western powers, which Britain took part in.

Cyber security has become a focal point of the strained relations. On Thursday, a British spy chief said that his GCHQ agency would "continue to expose Russia's unacceptable cyber behaviour", adding there would be increasing demand for its cyber expertise.

The Sunday Times also said that British spy officials had been preparing for Russia-backed hackers to release embarrassing information on politicians and other high-profile people since the attack on the Skripals.

Meanwhile the Russian Foreign Minister Sergei Lavrov said the nerve agent used to poison Mr Skripal could have been the BZ substance - which was never produced in the Soviet Union or Russia.

Mr Lavrov said experts from a laboratory based in the Swiss town of Spiez had analysed a sample of the substance used in the poisoning.

Citing a report from the lab dated March 27, Mr Lavrov said the evidence suggested the nerve agent used could be in the arsenal of the United States and Britain.

The global chemical weapons watchdog concluded on Thursday that the poison that struck down the former Russian spy and his daughter Yulia last month was a highly pure type of Novichok nerve agent, backing Britain's own findings.

British Prime Minister Theresa May has said it is highly likely that Moscow was behind the attack.