Afghan militants have attacked a supply depot outside the main international military base in southern Kandahar province, killing four security guards. Kandahar provincial spokesman Zalmai Ayubi said insurgents armed with explosives on Monday stormed the compound operated by Netherlands-based Supreme Group which supplies fuel to the military. Earlier in the day, militants attacked a district government center in central Ghazni province, triggering a gun battle that left one police officer and four militants dead. Three civilians suffered injuries as security forces repelled the assault.The fighting came a day after six suicide bombers attacked the compound of the governor of Parwan province, killing 22 people. Taliban militants claimed responsibility for Monday's attack.