At least 70 people have been killed by a huge suicide blast near a government compound 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 it had carried out the attack.
It is the largest attack since al-Shabab withdrew its forces from Mogadishu in August.
Rescue workers said more than 50 people had been injured in the blast. Many of the victims were soldiers and students who had been waiting at the education ministry.
The UN-backed transitional government condemned the attack and said no senior government officials were hurt in the blast.
Government members were meeting in the building near the blast site at the time.
"The attack shows that the danger from terrorists is not yet over and that there are obviously still people who want to derail the advances that the Somali people have made towards peace," it said in a statement.
The government statement set the number of dead at 15, but it was not clear whether this was only an initial count.
'Walls fell apart'
The blast struck outside a compound housing government buildings in Kilometre Four (K4) - a crossroads in central Mogadishu.
Police officer Ali Hussein told the Associated Press news agency that the vehicle had exploded after pulling up at a checkpoint on the way into the official compound.
At least 11 bodies burnt beyond recognition were lying on the ground. The main buildings and surrounding trees were on fire.
First-aid workers were carrying severely wounded people to ambulances. Two people with blood all over their legs were shouting for help.
People came rushing to the scene, but it is hard to identify the bodies. Some people were crying - it was very emotional.
Somali government soldiers then began shooting in the air to get the crowds to move as it was rumoured that other suicide vehicles may be in the area.
They are stopping and searching all cars. There are no vehicles moving in this area of the city.
Somalia's Planning Minister Abdullahi Godah Barreh told he was in his office when the blast hit.
"All of a sudden a huge, huge sound and all the furniture and all the windows and all the walls started falling apart," he said.
The vehicle carrying the explosives was big, he said, about an eight- or 10-tonne truck.
"The building that has been destroyed houses eight ministries, and you can imagine how crowded it would have been."
He said the area was protected, "but unfortunately, it was not good enough".
"Almost half of the cabinet sit in that building. So you can understand it was a good target for them - the terrorists."
BBC Somali's Mohammed Dhore in Mogadishu said vehicles were on fire, bodies lying in the street and shocked soldiers were randomly firing into the air in the aftermath.
He said it was the worst incident he had ever come across.
One aid worker said the force of the blast had thrown body parts hundreds of metres away.
Among those killed were soldiers guarding the offices and students who had been queuing for exam results at the education ministry, hoping to gain a scholarship to study in Turkey.
Ali Abdullahi, a nurse at Medina hospital in the city, said victims were being brought in with horrific wounds, including burns and lost limbs. Some had been blinded, he said.
"It is the most awful tragedy I have ever seen," he told.
"Dozens are being brought here minute-by-minute.
Most of the wounded people are unconscious and others have their faces blackened by smoke and heat."
