African Union troops and allied Somali forces bolstered positions Wednesday in the former Islamist bastion of Kismayo, residents said, a day after entering the Somali port city amid heavy explosions.Wary shopkeepers, who had shut down business since Al-Qaeda linked Shebab abandoned the city on Saturday, reopened for the first time, as patrols of Somali and AU forces moved through the town."There was shooting last night and a curfew in place until dawn, but today things have been quiet, no fighting, and we hope the situation is returning to normal," said shopkeeper Abdirasak Hassan."I have opened my shop but business is not so busy, as many people are staying in their homes to see if the (AU and Somali) forces are well disciplined."The hardline Shehab claimed responsibility for a heavy blast on Tuesday, while AU forces detonated several homemade bombs discovered as they seized control of the town's airport and harbour.Attackers also hurled a grenade into a tea shop late Tuesday, wounding seven people, according to residents.Long lines of Kenyan troops -- part of the AU mission -- marched in force into the southern port city on Tuesday, alongside a mix of Somali militia forces crammed into pickup trucks mounted with machine guns.