MAKHACHKALA, December 9 (RIA Novosti) - Law enforcement officers killed a gang leader and his wife early on Wednesday in a special operation in the Russian North Caucasus republic of Dagestan, the Federal Security Service (FSB) said.

"Members of an illegal armed unit were blocked in a private house. The militants opened fire when offered to surrender. A special operation got underway," an FSB spokesman said.

An assault rifle, a handgun, rounds of ammunition and a grenade were seized from the scene, no law enforcers or civilians were injured, he said.

Russia's mainly Muslim and ethnically diverse North Caucasus republics have been swept by an upsurge of violence recently, which has also swept neighboring regions, where hundreds of people have been killed in militant attacks and skirmishes between security forces and gunmen.

Moscow announced an end to its decade-long antiterrorism campaign against separatists in Chechnya in April, but has since had to step up the fight against militants as skirmishes and attacks on police and other officials have continued.

The president of the republic of Ingushetia was severely wounded and rushed to Moscow for treatment after a suicide bomber attacked his motorcade in June. Also in June, the interior minister was shot dead in Dagestan.

FSB chief Alexander Bortnikov said Tuesday police and other security forces have prevented 81 terrorist attacks in Russia's volatile North Caucasus this year.

Speaking at a session of the National Antiterrorism Committee, Bortnikov said 42 antiterrorist operations and a series of reconnaissance and search operations had been carried out in the region so far in 2009.