LONDON: British foreign minister Boris Johnson suggested on Thursday that corrupt Russians who owe their wealth to their ties with President Vladimir Putin could be targeted by British police in retaliation for a nerve attack on a Russian ex-spy.

Britain said on Wednesday it was expelling 23 Russian diplomats over the Novichok nerve agent attack on Sergei Skripal and his daughter Yulia, who collapsed in the southern English city of Salisbury on March 4 and remain in a critical condition.

Moscow denies any involvement and is expected to retaliate. The foreign ministry there said on Thursday morning it was still working on its response to the British measures, labeling London’s accusations against the Russian state “insane”.