(Adds International Contact Group, Sheikh Sharif) By Guled Mohamed MOGADISHU, Feb 8 (Reuters) - Attackers fired a rocket-propelled grenade at a pickup truck in Mogadishu on Thursday, wounding four people, in a reminder of the challenges facing the interim government trying to rule lawless Somalia. The latest guerrilla-style attack in the Somali capital came on the eve of a meeting of African and Western diplomats in Dar es Salaam on Friday. The International Contact Group on Somalia is expected to discuss reconciliation efforts and the sending of peacekeepers to the Horn of Africa nation, following a brief war between the Ethiopian-backed Somali government and rival Islamists. "We don't know what hit us, we only heard a big explosion and there was blood everywhere," said a witness in the truck hit by Thursday's attack. A wave of such strikes since Islamists were ousted from Mogadishu at the New Year have exposed the difficulties that President Abdullahi Yusuf's government faces in asserting its authority over a nation deprived of effective central rule since the 1991 overthrow of dictator Mohamed Siad Barre. Since defeating the Islamists, who had controlled most of south Somalia since June, the government and its Ethiopian allies have been attacked with mortars, grenades, gunfire and assassination attempts on a near-daily basis. The latest incident took place in a busy area near Mogadishu's Tarbuunka square, just after an Ethiopian vehicle had passed, the witness said. "There was an Ethiopian water-tanker ahead of us, maybe that was their target." Mogadishu police chief Ali Said said four people were hurt. "One was seriously wounded, he lost his leg in the attack," he told Reuters. On Wednesday, mortar bombs wounded at least eight people. A resident said two children were killed. Somali Deputy Defence Minister Salad Ali Jelle told Reuters Wednesday's attack came from a location close to an old military hospital and had been aimed at the port. Officials blame remnants of the Islamist movement, some of whom have vowed holy war. One of the group's most senior leaders, Sheikh Sharif Ahmed, seen by many as crucial in helping bring reconciliation to Somalia, arrived in Yemen on Thursday where officials said he would be allowed to stay.
