At least 13 people were killed on Sunday when Somalia's Al Shabaab Islamist militant group drove a car packed with explosives at the gate of a hotel, police and the rebel group said.

A Reuters witness said blood and pieces of flesh were spattered around the site of the blast which targeted the Jazeera hotel. The wreckage of four cars were nearby.

Al Shabaab, which said it was behind the blast, frequently launches bomb and gun attacks in the capital in its bid to topple Somalia's Western-backed government. The nation is trying to rebuild after two decades of conflict and chaos.

"It is a response to attacks and helicopter bombing against Al Shabaab by AMISOM and the Somali government," Sheikh Abdiasis Abu Musab, Al Shabaab's military operations spokesman, told Reuters.

AMISOM, the African Union's force in Somalia, has been battling the Islamist rebels with the Somali army. Al Shabaab has been pushed into increasingly smaller pockets of territory by a military offensive this year.

Major Nur Osoble, a police officer, told Reuters a suicide car bomb rammed the gates of the hotel, damaging the facade. Another senior police officer said at least four people were killed, while an ambulance worker said eight were wounded.

Jazeera hotel has been targeted on previous occasions. The blast on Sunday sent a plume of smoke rising above the coastal capital. Sporadic gunfire was heard shortly after the attack.

Al Shabaab, which wants to impose its strict interpretation of Islam on Somalia, killed a lawmaker, his bodyguard and an official from the prime minister's office on two attacks on Saturday.  - Reuters