American Helped Bomb Somalia Base, Web Site Says

NAIROBI, Kenya — A Somali Web site is claiming that one of the suicide bombers who attacked an African Union base last week in Somalia was from the United States, which, if true, would make him the second known American to carry out a suicide attack.

According to Dayniile.com, a mostly Somali-language Web site, the bomber lived in Washington State until 2007, when he left the United States to join the Shabab, a terrorist group with growing ties to Al Qaeda. Several suicide bombers penetrated an African Union base in Mogadishu, Somalia’s capital, Sept. 17, killing more than 15 peacekeepers, including the second in command of the 5,000-strong African Union mission in Somalia.

The bombers used United Nations trucks to slip into the base; they apparently had inside information because they struck precisely at a time when high-ranking Somali officials were meeting with African Union commanders to plan an offensive. Some witnesses said the bombers spoke English.

The Shabab took responsibility for the attack. But on Thursday, Shabab officials, when asked about the possible Somali-American connection, said they would not reveal the bombers’ identities.

“We’re not giving out any of that information,” said one Shabab official, who spoke anonymously because he was not authorized to speak with journalists.

The Somali Web site listed a Seattle phone number for the bomber’s father, but the number is apparently not in service.

The Web site is known among Somalis as usually reliable. It focuses on news of interest to the Mursade subclan, which has contributed many fighters to the Shabab.

The Shabab are waging an intense guerrilla war against Somalia’s moderate Islamist transitional government and are trying to turn Somalia into a factory for global jihad. According to American and Somali officials, several high-ranking Qaeda agents are training Somali militants and recruiting terrorists from around the world to fight in Somalia.

According to F.B.I. officials, around 20 young Somali-American men have disappeared from the Somali community in Minneapolis over the past two years to join the Shabab.

One of them was Shirwa Ahmed, who blew himself up in northern Somalia last October, becoming the first known case of an American suicide bomber. The F.B.I. director, Robert S. Mueller III, has said that Mr. Ahmed was “radicalized in his hometown in Minnesota.”

Another Somali-American from Minnesota, Mohamed Hassan, 21, was killed during fighting in Mogadishu several weeks ago.