At least 55 people have been killed by a huge suspected suicide blast near government buildings in the Somali capital, Mogadishu, say officials.

Eyewitnesses said a truck carrying explosives was driven into a gate near a government ministry and detonated.

A spokesman for the Islamist militant group al-Shabab told the BBC it had carried out the attack.

A BBC correspondent at the ministry said there were bodies on the ground and soldiers firing into the air

He said it was the worst incident he had ever experienced.

The blast struck outside a compound housing government buildings in the Kilometre Four district.

An official with Mogadishu's ambulance service, Ali Ruse, said 65 bodies had been recovered and at least 50 other people had been injured.

"Some are still lying there. Most of the people have burns," he told Reuters news agency.

Al-Shabab, which has links to al-Qaeda, controls large swathes of south and central Somalia.

It retreated from Mogadishu two months ago, but analysts said that without a front line it was likely to begin carrying out more suicide attacks.