"Activities of 48 staff officers of foreign intelligence services have been stopped, as well as actions of 101 local agents of foreign special services," Alexander Bortnikov told an annual meeting with the Russian press.

He said six foreign staff officers and three agents had been "caught red-handed", and nine foreigners accused of spying had been expelled.

The FSB, a target of public criticism in 1990s, has seen a resurgence under ex-President Vladimir Putin, an ex-KGB spy whose two terms as Kremlin chief ended this year.

Putin and top FSB officials have often said that the West, suspcicious of Russia's revived ambitions, has stepped up spying activities in the country. Western officials counter that Russia is itself conducting aggressive espionage abroad.

Putin has more than once accused Western special services of funding opposition groups and non-governmental organisations to destabilise the political situation in the country. Opposition groups and NGOs have denied such accusations.

Dmitry Medvedev, who replaced Putin as president in May, is a former corporate lawyer and has no intelligence background. But under him, the FSB has faced a new foe, the former Soviet republic of Georgia.

In August, Russia sent troops to repel Georgia's attempt to recapture its separatist, pro-Russian province of South Ossetia. The two countries fought a five-day war in which Georgian forces suffered a heavy defeat.

Bortnikov said the FSB had uncovered a network of agents of the Georgian special services in Russia.

He said a Georgian citizen suspected of being one of the organisers had been arrested. Five Russian citizens, suspected to be members of the ring, had been charged with high treason.

A senior Georgian lawmaker said he knew of the detentions, but denied the suspects had operated on Tbilisi's behalf.

"I've heard about this group being charged and arrested in Russia. It happened before the war," said Givi Targamadze, head of the Georgian parliament's defence and security committee.

"Of course we have nothing in common with these people and they are, of course, not our spies, but Russia is making such statements in order to justify its attitudes towards Georgia and to show us in a bad light," he told Reuters.