Russia's Federal Security Service (FSB) announced Thursday that it had uncovered a plot by the US National Security Agency (NSA) to use previously unknown "malware" to penetrate specially made holes in Apple phones.

The FSB announced that several thousand Apple phones were infected, including the phones of domestic Russian subscribers. The Russian agency added that phones belonging to foreign diplomats based in Russia and the former Soviet Union, including phones from NATO members, Israel, Syria and China, were targets of US infiltration.

"The FSB uncovered an intelligence operation by the US special services using Apple mobile devices," the FSB said in a statement. Apple and the NSA did not respond.

The FSB said the disclosure showed the close relationship between Apple and the National Security Agency, the US agency responsible for intelligence and security of US cryptography and communications. – Russian, and their citizens," it was reported.

Unusually, the FSB noted that the plot was uncovered with the help of the Federal Guard Service, the agency that protects Russia's leaders.