MOSCOW, March 11 (Xinhua) -- The Russian Federal Security Service (FSB) said it foiled an attempt to launch a terrorist attack in southwest Russia's Saratov region on Sunday, killing several perpetrators.

During a search operation, the members of a deep-cover terrorist cell opened fire after security forces tried to stop their car, according to a brief FSB press release.

The FSB said the perpetrators received fatal injuries in a cross-fire, but it did not disclose the number of the deaths.

Pistols, a homemade grenade and an improvised explosive device of about 3 kg of TNT equivalent were found at the scene, it said, adding that an immediate investigation is underway.

Russian regions in or near the North Caucasus are vulnerable to terrorist attacks as extremism has been plaguing the regions for years.