Islamic insurgents posing as U.N. personnel detonated homicide car bombs in an African Union peacekeeping base Thursday to avenge a U.S. commando raid that killed an Al Qaeda operative.

Witnesses and officials said the bombings and a counter-strike from the AU base killed at least 16 people, including four bombers, and wounded dozens.

The sophisticated homicide attack underscored links between Al Qaeda's terror network and Somalia's homegrown insurgency. Many fear this impoverished and lawless African nation is becoming a haven for Al Qaeda — a place for terrorists to train and plan attacks elsewhere.

An hour after the bomb attack there was more bloodshed. Missiles fired from the peacekeepers' airport base exploded in insurgent-controlled areas of the capital.

An Associated Press photographer saw a young woman and a girl dead on the street, their bodies bloodied from their wounds.

Ali Muse of the Mogadishu ambulance service said the missiles killed seven people and wounded 16.

The homicide bombings are a hallmark of Al Qaeda that can be traced to training from militants like the operative killed this week by helicopter-borne U.S. special forces, said Ted Dagne, a Washington-based Africa specialist.

Homicide attacks were virtually unknown in Somalia before 2007, even though the nation has been wracked by war for almost two decades.

"Al Qaeda provided the training as well as the brainwashing," Dagne told the AP. "Never in Somali culture, never during 19 years of war, was homicide bombing used as a tool. This is new."

There have been about a dozen homicide bombings since the Islamic insurgent group al-Shabab stepped up its attacks against the Western-backed backed government in 2007.

Al-Shabab controls much of Somalia and operates openly in the capital, confining the government and peacekeepers to a few blocks of the city. The U.S. and the U.N. both support Somalia's government and the African peacekeeping force.

The homicide bombers arrived at the airport in U.N. cars packed with explosives and drove onto the main base of the AU peacekeepers before setting off two huge blasts that shattered windows over a wide area and shrouded the sky in black smoke.

An airport security officer said soldiers guarding the base waved in the trucks because they were U.N. vehicles. Prime Minister Omar Abdirashid Ali Sharmarke confirmed the cars had been stolen.

"When the cars entered one of them sped toward a petrol depot and exploded," the security officer said, asking that his name not be used because he is not authorized to speak to the media. "The other one exploded in a nearby area."

A witness, who spoke on condition of anonymity for fear of reprisal, said there were 11 bodies at the AU base. But the AU said nine people were killed there: four homicide bombers and five officials from the Somali government and the AU peacekeeping force, including its Burundian deputy commander.

At least one American was wounded by the bombings, according to a police official in Nairobi, Kenya, where several of the wounded were flown. The official cited the flight manifest, but did not give the man's name. The official spoke on condition of anonymity because he was not authorized to speak to the media.

U.N. Secretary-General Ban Ki-moon said at least 30 wounded personnel were being evacuated from the country. "I condemn this attack — this terrorist attack — in the strongest possible terms," he said.

Al-Shabab, a powerful Islamist group with foreign fighters in its ranks, claimed responsibility for the bombings and said the attack was in retaliation for the death of Saleh Ali Saleh Nabhan. He was killed Monday in southern Somalia by U.S. special forces who blasted his vehicle with machine-gun fire from helicopters.

The AU force has long lamented that it is undermanned. Out of a planned 8,000 troops, there are about 5,000 troops from Uganda and Burundi.

Somalia has been ravaged by violence and anarchy since warlords overthrew dictator Mohamed Siad Barre in 1991 and turned on each other. Piracy has flourished off the Somali coast, making the Gulf of Aden one of the most dangerous waterways in the world.

Sharmarke appealed to the international community for help.

"Support Somalia and its government in fighting the people behind these terrorist attacks," he said.