In all, 1,689 militants and foreign mercenaries have been destroyed this year in Chechnya during joint operations with the involvement of units of the Federal Security Service, the RIA Novosti correspondent quotes FSB director Nikolai Patrushev as saying on Tuesday. Patrushev said that among the militants are warlords Abu Darr, Abu Umar, Arbi Barayev, Abu Yakub and Magomed Tsagarayev. Operatives arrested international terrorist Muhammad Abdel Aziz Abdel Wahab of Iran. Last autumn the Krasnodar regional court sentenced him to 12 years in prison on three articles of the Criminal Code of the Russian Federation. In FSB special operations in the North Caucasus, 90 installations of illegal armed formations have been destroyed in 2001 -- retransmitters, depots, bases and underground communications, reported Nikolai Patrushev. Operatives have also discovered the propaganda archives of the separatists' ideologist Movladi Udugov, added Patrushev. He said that the struggle against international terrorism is the most important aspect of work of the Russian Federal Security Service.