NAIROBI — The suspected leader of Al Qaeda in Somalia was killed in an American air attack on yesterday, witnesses and the Pentagon said.

The head of the Shabaab insurgent movement, Aden Hashi Ayro, died when his home town of Dusamareb was bombed by up to four planes.

At least another 30 people were killed in the strike, which took place in the early hours.

The raid was the biggest blow against the Islamist group, which is waging a guerrilla campaign against Somalia’s government and its Ethiopian allies, since the collapse of the powerful Islamic Courts Union in December 2006.

“The U.S. Central Command has conducted an attack against a known Al Qaeda target and militia leader in Somalia,” a spokesman, Lieutenant Joe Holstead, said.

Ayro’s death is likely to bolster the Western-backed Somali government’s efforts to stem a rebellion that has been gaining ground under the leadership of the Afghanistan-trained terrorist.

Violence had intensified in recent weeks, with scores of deaths in Mogadishu and a series of hit-and-run raids by the Islamists on towns.

But the raid will enrage Ayro’s fellow fighters, who say they are waging a jihad to eject Ethiopian troops who helped the Somali government to overthrow the Courts Union.

“It’s a very significant strike,” a Western diplomat in Nairobi said. “Ayro is most likely a key cog in any links between Al Qaeda and Somalia and taking him out will make it very difficult for the organization to expand into Somalia.”

However, he added, the attack would likely coalesce anti-American feeling and could bolster resources for the insurgency in Somalia.

A Shabaab leader, Mukhtar Robow Adumansur, said there would be revenge attacks against Western interests in East Africa.