Assailants on Sunday rained rockets on an army base, killing four, and assassinated the son of a tribal elder who has helped track down militants, said intelligence officials in the tribal areas. Two suspected militants were killed at a checkpoint, a security official said. On a road in South Waziristan Agency, masked gunmen killed the 20-year-old son of Malik Khadin, the prominent elder who led a tribal militia in a search for militants last year, an intelligence official said on condition of anonymity. The elder Khadin survived an assassination attempt in August, but four people riding with him in a car were killed.In North Waziristan Agency, 20 rockets were fired before dawn on a base in Mir Ali, a town east of Miranshah, said another intelligence official. A soldier and three government employees died sleeping in their barracks, and four others were injured, the official said. Five other rockets landed in two villages nearby, damaging some homes, he said. At a roadblock east of Miranshah, security forces fatally shot two local tribesmen who would not give up their AK-47 rifles while their pickup truck was searched, a security official in Miranshah said on condition of anonymity. Two other men, one of whom was injured in the shooting, were arrested, the official said. Meanwhile, troops supported by helicopter gunships continued their search for militants in Khati Kalla village near the Afghan border, residents said.