At least 100 people were killed and nearly 50 injured when a truck bomb went off outside the government buildings in the heart of Somalia's capital Mogadishu on Tuesday.

Al Qaeda-linked al Shabaab rebels claimed responsibility for the attack.

Somalia ceased to exist as a single state in 1991 with the downfall of the heavy-handed regime of President Siad Barre. The federal government is in control only in the capital and surrounding areas with local clans and Islamic radicals running the rest of the East African country.

While an investigation is underway, experts say the blast was caused by a car bomb. The attack was claimed by al-Shabaab anti-government group linked to al-Qaida. Al-Shabaab insurgents had more than once carried out attacks in Somalia. A spokesman for the group confirmed that the Mogadishu attack was targeting a government compound.

The car bomb exploded at the security checkpoint at the entrance to the area, where different government institutions are located, including the prime minister`s residence, and the Foreign Ministry.

At the moment of the attack, the UN-backed Transitional Federal Government was holding a session inside one of the buildings. However, there have been no reports so far on whether some of the officials were among the victims.