A suicide bombing has struck Somalia's capital, Mogadishu, killing five people including the bomber, with the armed group al-Shabab quickly claiming responsibility.

Witnesses reported a loud explosion, followed by gunfire and plumes of smoke, in Waaberi district on Sunday.

The area is close to the heavily fortified international airport.

 
Residents survey aftermath of the bombing in Mogadishu's Waaberi district [Mustaf Abdi Nor Shafana/Al Jazeera]  

Witnesses told Al Jazeera the attack targeted Somalia's National Intelligence and Security Agency and that security forces opened fire to disperse approaching onlookers.

Ahmed Adan, a Somali police official, told AFP news agency: "There was a car bomb explosion near the Afisiyone area.

"We are getting information that a suicide bomber rammed a car laden with explosives into a pickup truck."

Mohamed Yusuf, Interior Ministry spokesperson, said security agencies had received information about a car laden with explosives and had been following it.

"It exploded and four civilians were killed besides the bomber."

Speaking to Al Jazeera, Abu Musaab, military-operations spokesperson of al-Shabab, said: "We conducted an operation against the apostates - including white mercenaries - in Mogadishu.

"There were heavy casualties. We will give more details later."

Last month al-Shabab gunmen attacked the main African Union base in Mogadishu leaving at least eight people dead. The AU base hosts UN offices and embassies.

Sunday's blast comes days after a US air strike killed al-Shabab's intelligence chief, Abdishakur Tahlil.

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

Source: Al Jazeera and agencies