Officials say Pakistani security forces launched an operation targeting militants in a restive northwestern district bordering Afghanistan following a surge in attacks and sectarian strife. It is the first large-scale operation in the area in recent years. The latest attack in Kurram was on Friday when unidentified gunmen ambushed and burned aid trucks, killing two security personnel and at least five drivers. The district has been cut off from the rest of the country since November after authorities blocked roads following clashes between heavily armed Shiite and Sunni tribes. A spokesman for the provincial government said on Monday the operation became “inevitable” following the spike in violence.