World Bulletin / News Desk

Moscow said Friday it could hit back at Britain at "any minute" with its own raft of punitive measures after the West blamed Russia directly for a nerve agent attack on a former double agent.

"All the steps will be well thought out," he told reporters.

In a rare joint statement, the leaders of Britain, France, Germany and the US on Thursday condemned the attack on former double agent Sergei Skripal and his daughter Yulia as an "assault on UK sovereignty".

Moscow has vehemently denied it had a hand in the poisoning of its former spy in the cathedral city of Salisbury early this month.

Britain's key allies closed ranks against Putin after British Prime Minister Theresa May announced the expulsion of 23 Russian diplomats and suspended high-level contacts, among other measures.

Russia said earlier this week it would expel British diplomats in response to London's move as well as adopt other measures that the Kremlin said would "most suit Moscow's interests."

"Of course we will," Russian Foreign Minister Sergei Lavrov told journalists when asked whether Moscow would respond in kind. 

He did not provide further details.

Moscow's ambassador to Britain Alexander Yakovenko said that the majority of the Russian diplomats would leave the country next week.

The crisis unravelled in the thick of a Russian presidential campaign, with Putin expected to win a fourth Kremlin term on Sunday.