More than 70 people were killed as Somalia's al-Shabaab rebels hit the centre of Mogadishu with a truck bomb.

Another 150 people were wounded in the blast, which has been denounced by Somali President Sheikh Sharif Ahmed as a cruel and inhumane act of violence.

A truck laden with drums of fuel rammed a checkpoint outside a compound housing government ministries where students had gathered to register for scholarships offered by Turkey.

U.N. Secretary General Ban Ki-moon said he was appalled by the vicious attack.

Al-Shabaab insurgents pulled most of their fighters out of Mogadishu in August, allowing government troops and African Union soldiers to seize much of the capital. But the rebels vowed to still carry out attacks on government installations.

The al-Shabaab insurgents who carried out the attack later warned Somalis to stay away from government buildings and military bases.