Aden Hashi Ayro, a slight, Afghanistan-trained Islamic extremist who was thought to be in his early 30s, led the group known as al-Shabaab - "the youth" - which last month was added to the U.S. list of terrorist organizations because of its alleged ties to al-Qaeda.

Sheikh Muhktar Robow, a spokesman for the extremist group, confirmed Ayro's death.

Lt. Joe Holstead of the U.S. Central Command said that the military had carried out an attack on "a known al-Qaeda target and militia leader" near the town of Dusamareb, about 300 miles north of the capital, Mogadishu.

Another U.S. official with knowledge of the operation confirmed that Ayro had been killed. That official requested anonymity to discuss a sensitive military operation.

The predawn strike, which residents said killed more than a dozen other people, was the fourth time in 16 months that the U.S. military has bombarded reputed Islamist hideouts in Somalia. But it would be the first time that a strike netted a major U.S. target.

Ayro developed a reputation as one of the most dangerous men in East Africa as the leader of al-Shabaab, the militant wing of an Islamic fundamentalist movement that took over Mogadishu in 2006 and imposed religious law.

Neighboring Ethiopia sent troops into Somalia in December that year, driving movement members from the capital and parts of southern Somalia. But al-Shabaab continues to wage an Iraq-style insurgency.

Ahmed Samatar, a Somalia expert at Macalester College in St. Paul, Minn., said Ayro's death would not significantly weaken the insurgency because anger against the Ethiopian military occupation - and U.S. support for it - runs too deep.

"I have little doubt that the resistance will continue until there is a full withdrawal of Ethiopian troops out of Somalia and a new legitimate and competent national government is established," Samatar said.

Ayro's killing also comes amid U.N.-backed peace talks, which are slated to be more inclusive than previous rounds and offer a slim hope of bringing together the disparate groups in the armed opposition, including some Islamists.

Yesterday's attack damaged the talks, Rashid Abdi, an analyst at the International Crisis Group, told the Associated Press.

Residents of Dusamareb said four low-flying fighter planes buzzed the town about 4 a.m. and slammed several missiles into a series of houses, including one housing Ayro and several other extremists.

"We so far collected 15 dead bodies, some of them shattered to pieces," Mohamed Daud Ali, a 41-year-old resident, said by telephone. "Some victims were taken to the hospital and treated for terrible burns."

Islamist officials said that Ayro had been in Mogadishu commanding the extremist group until a few days ago, when he arrived in Dusamareb, a well-known hideout.

The invasion by neighboring Ethiopia - backed by U.S. military and intelligence support - put a U.N.-backed transitional government in power in Somalia.

Under Ayro's leadership al-Shabaab quickly regrouped. Since January 2007, it has been blamed for a string of roadside bombings, assassinations and guerrilla attacks on Somalian and Ethiopian forces.

The violence has plunged Somalia, which has not had a functioning government since 1991, into crisis and forced an exodus from Mogadishu, a once-pretty seaside city that now looks like a postapocalyptic ghost town.

U.S. officials say Ayro protected the al-Qaeda operatives who carried out the 1998 bombings of the U.S. embassies in Kenya and Tanzania, which killed more than 220 people, as well as the 2002 car bombing of a Kenyan resort hotel frequented by Israeli tourists.

Previous U.S. strikes in Somalia have drawn criticism from human-rights groups, which said that most of the victims were civilians.