Mogadishu: Islamist rebels detonated a car bomb at the entrance of a hotel in the Somali capital on Friday and then stormed inside where politicians had gathered, killing at least 10 people including a lawmaker and lightly wounding two ministers.

Al Shabaab, which claimed responsibility for the attack, aims to topple the Western-backed federal government and impose its strict version of Islamic sharia law on the Horn of Africa nation that is struggling to rebuild after two decades of war.

The suicide attack targeted the Central Hotel around midday on Friday, typically a busy time for hotels as it is the Somali weekend. Ambulances wailed as they raced to the scene where a huge plume of smoke rose above the Indian Ocean coastal city.

"We are behind the attack," Sheikh Abdiasis Abu Musab, al Shabaab's military operations spokesman, told Reuters. "We targeted government officials in the hotel; this is part of our operation in Mogadishu."

"First the car bomb exploded at the gate of the hotel, then a suicide bomber blew himself up in the hotel compound," police Major Nur Mohamed told Reuters. "There were ministers and legislators inside the hotel."

He said at least 10 people had been killed, including a lawmaker, security officers and civilians. "But the death toll may rise," he added. Gunshots were heard for a short period inside the hotel after the attack.

Farah Abdullahi, a police captain, said Deputy Prime Minister Mohamed Omar Arte and Ports and Marine Transport Minister Nur Farah Hirsi were lightly wounded. He earlier wrongly identified one minister as Transport Minister Ali Ahmed Jamac.

A presidential spokesman said President Hassan Sheikh Mohamud condemned the assault as a "terrorist attack".

Information Minister Mohamed Abdi Hayir Mareye told a radio station that "many died" including a lawmaker and the deputy mayor of Mogadishu. He said more details would follow.

Al Shabaab once ruled much of Somalia but it has been slowly pushed out of strongholds across the country. However, its guerrilla-style gun assaults and suicide bombings continue to exert pressure on the government to improve security.

A military campaign launched by African Union peacekeeping forces and the Somali government forces last year ousted al Shabaab from Mogadishu in 2011 and from major coastal towns.

But persistent guerrilla-style attacks in Mogadishu, while less frequent, have complicated the government's efforts to secure the nation for a referendum on a new federal constitution and a presidential election during 2016.