Russia's Federal Security Service (FSB) on Thursday uncovered what it called a plot by the US National Security Agency (NSCA) using previously unknown malware to penetrate specially manufactured vulnerabilities in Apple phones.

Russia's Federal Security Service (FSB) said several thousand Apple phones were infected with the malware, including subscribers' phones inside Russia.

He said the targets included the phones of foreign diplomats living in Russia and countries that were part of the former Soviet Union, including countries currently in NATO, Israel, Syria and China.

"Russia's Federal Security Service revealed that prominent US security services have made intelligence moves using Apple phones," the Russian security service said in a statement.

Apple and the U.S. National Security Agency did not immediately respond to requests for email comment outside of normal U.S. business hours.

The Russian agency said the plot showed the close relationship between Apple and the U.S. National Security Agency.

Apple provides U.S. intelligence agencies with a wide range of opportunities "to monitor anyone of interest from the White House and its partners in anti-Russian activities and (to monitor) their citizens," the agency said.

Unusually, Russia's Federal Security Service (FSB) said the Federal Guard Service, the agency responsible for securing Russian leaders and leaders, helped uncover the plot.