At least five people, including the bomber, died in an attack on a popular restaurant in Mogadishu on Monday, police official Ali Hassan Kulmiye told German Press Agency (DPA).

The targeted restaurant is frequented by government security forces and port workers in the Somali capital. Hassan Kulmiye noted that most of the dead were civilians.

Police officer Abdirahman Mohamed said the restaurant's security guard, who had stopped the suicide bomber at the entrance, was among the dead.

The powerful blast could be heard in many parts of the city. It sent a thick plume of black smoke into the sky.

"I narrowly escaped with slight injuries on my face and arms," Ahmed Abdi, a port worker who had been having lunch at the restaurant when the explosion occurred, told DPA.

Abdi said he saw several bodies, "but there were many people in the restaurant and casualties may be higher."

Terrorist group al-Shabab claimed responsibility for the attack on their media platform Radio Andalus. The group, which seeks to establish an extremist state in Somalia, also claimed to have killed nine people, four more than the official figure.

The restaurant, close to Mogadishu port, is popular with security officers and government officials working in the nearby area, who are regularly targeted for assassination by al-Shabab.

Al-Shabab's claims have not been verified, but the group is known to regularly launch attacks on government buildings, hotels and restaurants in the volatile Horn of Africa nation.

The group is affiliated with the international al-Qaida terrorist network.

U.S. forces are partnering with African Union troops, AMISOM, and the Somali forces in combined counterterrorism operations in the troubled East African country.