At least seven people, mostly Somali soldiers, were killed Saturday in bomb explosions in the Somali capital Mogadishu, officials and witnesses said. A roadside bomb planted under a tree killed four soldiers and one civilian in northern Mogadishu\'s Karan district while at least two soldiers died in a separate grenade attack in Bakara market. \"Four soldiers were killed when a bomb planted in the shade of a tree was detonated. One civilian was also killed in the attack and the security forces are conducting investigations,\" Abdirahman Mumin, a Somali security official said from the scene of the blast. He attributed the attack to the Somali Islamist extremists who abandoned fixed positions in the capital last August and who have since concentrated on guerrilla tactics. \"I think Al-Shebab planted the bomb during the night when nobody was in the area,\" he said. In a second attack, unknown assailants hurled grenades at Somali soldiers who were pulling down illegal buildings near Bakara market, killing at least two of them. \"There was a heavy explosion in Bakara market as the soldiers were destroying illegal buildings. It was a grenade attack and I saw the dead bodies of two soldiers,\" Dahir Moalim, a witness, said. Another witness, Shamso Mohamed, confirmed he had seen two soldiers killed in Bakara market. Somali forces and an 11,000-strong African Union force, AMISOM, have made significant gains in recent months against Shebab militants, but despite the lull in street fighting, Mogadishu has been plagued by a series of suicide and grenade attacks since the Shebab reverted to guerrilla tactics. Earlier this month a mortar shell that was fired into a crowded neighbourhood of the city killed seven civilians, including two children. Last month a suicide bomber blew herself up during an address by Somalia\'s prime minister in Mogadishu, killing four people including the country\'s Olympic and football bosses. And in March a suicide bomber killed at least five people in an attack at the heavily guarded presidential palace. Somalia\'s transitional administration has until August to set up a permanent government. UN powers earlier this month expressed concern that it is lagging behind on its timetable. The mandate of the transitional government has already been extended several times, and Western nations are saying it cannot be extended again. Fighting erupted in Somalia in the late 1980s, escalating into a brutal civil war following a 1991 coup, with rival militias, warlords and Islamist fighters battling ever since for control of the Horn of Africa nation.