Two suicide bombers attacked the port in the Somalia capital Mogadishu Thursday, killing two civilian workers and also losing their own lives, witness and officials said. One of the suicide bombers blew himself up and security forces shot the other dead, they said. \"Two suicide bombers attacked the port, sneaking in through a side entrance,\" said Mohamed Ibrahim, a Somali security officer. \"One of them was gunned down by security forces while the other detonated himself,\" he said. Witnesses said two civilian port workers were also killed. \"I saw the dead bodies of two workers who were killed in the explosion,\" said Osman Yusuf. No one claimed responsibility for the attack but suspicion fell on Shebab Islamists who have vowed to topple the transitional government and chase out African Union troops supporting it. The Shebab have been losing ground in the capital in recent months as pro-government troops and their African Union force in Somalia (AMISOM) backers have clawed back several key positions. Regional security sources said part of the Shebab\'s strategy in the face of AMISOM\'s advance was to step up suicide attacks. Somali police said at the end of May they had learned of plans for a series of such attacks in Mogadishu. On May 30 two Ugandan troops from AMISOM were killed in a suicide attack on their base in south Mogadishu.