A suicide car bomber blew himself up near a moving convoy of Somalia's U.S.-trained elite forces in Mogadishu, killing at least four people, a Somali police officer said Sunday.

The attacker drove his bomb-laden car into a convoy of troops on the airport road in the capital, killing mostly pedestrians walking along the road, Capt. Mohamed Hussein said.

Mohamed Yusuf, the spokesman of Somalia's National Security Ministry, said the government had information about the attack, and the car bomb was detonated while the attacker was being pursued.

"We shall continue preventing such attacks, however we ask people to work with us," he told reporters in Mogadishu.

The Alpha Group troops are part of Somalia's intelligence forces and often carry out operations against militants in Somalia.

There was no immediate claim of responsibility for the attack. Somali militant group al-Shabab is waging an insurgency against Somalia's government.

The blast comes days after a U.S. airstrike killed al-Shabab's intelligence chief, Abdishakur Tahlil.

Somalia's government is struggling to rebuild the country after decades of conflict sparked of by the 1991 ouster of dictator Siad Barre.