MOGADISHU - At least six people were killed and 22 injured when an explosion went off outside a busy hotel in Somalia's capital on Thursday, followed by gunfire, police and rescue services said.Al Qaeda-linked al Shabaab militants claimed responsibility. The group carries out frequent bombings and other attacks in Mogadishu in a campaign to topple Somalia's Western-backed federal government."The death toll has risen to six and the number of injured people to 22," said Abdikadir Abdirahman, director of Amin ambulances.Al Shabaab's military operation spokesman said his group had carried out the attack."We are behind the blast. We killed ten people including soldiers and officers," he said.Reuters TV footage showed civilians carrying the wounded on makeshift stretchers to the ambulances from Amin, which is the city's sole ambulance service and is privately-run, as security forces stood around with guns.At least five three-wheel scooters that were passing on the road had been overturned by the blast.