At least two frontier constables were killed while four others were injured in a mortar attack here in South Waziristan, a private TV channel reports Sunday. The mortar fired from some unknown location hit Frontier Constabularys Fort Tanai in Army Colony area of Wana, killing two FC personnel and injuring four others. Meanwhile, at least eight suspected militants were killed in clashes with security forces during their ongoing operation in Saam and Langerkhel areas. An unknown number of militants were also killed in Pak Armys air strikes in South Waziristan early Sunday. Military jet planes pounded suspected hideouts of Taliban militants in Ladha area of the agency. Number of casualties have not yet been ascertained, claimed the channel.