MOGADISHU — Somalia’s al-Qaeda-linked rebels struck at the heart of the capital Mogadishu on Tuesday, killing scores of people with a truck bomb in the group’s most deadly single attack since launching an insurgency in 2007.

Mogadishu’s ambulance coordinator Ali Muse said at least 70 people had been killed by the blast. Initial official estimates were lower, but were expected to rise as the dead and wounded had been taken to a number of sites in the capital.

Witnesses said a truck exploded at the gate of a compound housing government ministries in the K4 (Kilometre 4) area of Mogadishu, where students and parents had gathered to await the results of scholarship exams.

The twisted axle from the truck lay on blackened soil. A body draped with a red shawl lay nearby. People used corrugated iron, rugs and white sheeting to carry corpses away from the devastation at a normally bustling junction.

Ambulances rushed to and fro past twisted, charred trees and a burnt out car. Hundreds of parents stood weeping outside the Madina Hospital in Mogadishu after being denied access for security reasons and nurses said they were overwhelmed.

“I was among the first people to arrive here moments after the explosion. I looked around and reassured those who were still alive,” said witness Halma Abdi.