A suicide car bomb attack by Islamist group al-Shabab has killed four people in the Somali capital Mogadishu, officials say.
Witnesses said the blast was close to the international airport, where African Union troops, UN staff and several Western embassies are based.
Plumes of black smoke were seen in the area and the sound of gunfire was heard shortly after the explosion.
Security has improved but al-Shabab still attacks Mogadishu regularly.
A Somali official told the AFP news agency that security forces were alerted to the threat of a car bomb shortly before the blast.
“We had information about this car laden with explosives and we have been following it. But it detonated and four civilians were killed, and the bomber,” interior ministry spokesman Mohamed Yusuf said.
The attack targeted a convoy of US-trained Somali intelligence forces known as the Alpha Group, Somali police officer Mohamed Hussein told AP news agency.
Witnesses say they were shocked by the size of the explosion.
“I’m not sure how many casualties there were yet, but I was really panicked by the force of the blast,” said Mohamed Waberi.
A military spokesman for al-Shabab, Sheikh Abdul Aziz Abu Musab, confirmed that the militants had carried out the attack, AFP reported.
Sunday’s blast comes just days after a US airstrike killed the group’s intelligence chief, Tahlil Abdishakur.
Security officials had said on Wednesday that Abdishakur was part of a unit responsible for suicide attacks.
Last month al-Shabab insurgents infiltrated the airport compound, killing three AU peacekeepers and a civilian contractor.
Earlier in December, at least six people were killed when al-Shabab attacked a UN convoy near the airport.
The AU has about 22,000 troops in the country drawn from Burundi, Djibouti, Ethiopia, Kenya, Sierra Leone and Uganda.
Various armed groups have been battling for control of Somalia since the overthrow of President Siad Barre in 1991.