The revelation, made by an FSB spokesman who accused the US agency of crossing a “red line” in its attempt to recruit turncoats among Russian spy agencies, will up the ante in the unfolding spy scandal that emerged earlier this week when Russia detained and expelled an alleged CIA agent working undercover as third secretary at the US embassy in Moscow.

Russian officials, including President Vladimir Putin’s foreign policy advisor, have taken pains to say they believe the scandal will blow over quickly.

Publicly revealing the CIA station chief proves that some inside the Russian government believe otherwise and is likely to prompt an angry response from Washington.