Police said on Tuesday they had arrested two militants in connection with the weekend killing of two employees of Aga Khan Health Services. Masked gunmen on Sunday stormed the office of the aid agency in Chitral, killing a security guard and a driver and setting fire to several vehicles. Gul Mohammad Khan, a police officer in Chitral, said two activists of a banned Sunni Muslim group Harkat-ul Mujahideen had been detained on suspicion of involvement in the attack. The Aga Khan's aid network runs health services in Chitral and other parts of northern Pakistan.