At least eight people have been killed in Somalia's capital after Islamist militants launched a suicide attack on a UN security convoy using a vehicle laden with explosives.
The Islamist group al-Shabab claimed responsibility for Thursday's huge blast which rocked Modadishu and injured at least 23 people, including school students, sending a column of smoke above the city.
Gunfire echoed around the scene, witnesses said.
It was not immediately clear if any UN personnel were among those killed or injured in the huge blast, which targeted the convoy as it passed near the site of a school.
UN officials did not immediately respond to requests for comment.
Police spokesman Abdifatah Aden Hassan said a suicide bomber in an SUV full of explosives had targeted a UN security convoy.
"We counted eight dead people and 17 others including 13 students injured," he told reporters.
Aamin Ambulance service evacuated at least 23 people who were injured in the blast, director Abdikadir Abdirahman told Reuters.
The blast near the K4 junction in the heart of Mogadishu was so large that walls of the nearby Mucassar primary and secondary school collapsed. Cars were mangled in the explosion.
A nurse who was pulled from hospital rubble described a large explosion followed by gunfire.
"We were shaken by the blast pressure, then deafened by the gunfire that followed," said Mohamed Hussein, a nurse at the nearby Osman Hospital.
"Our hospital walls collapsed. Opposite us is a school that also collapsed. I do not know how many died," he said.
Al-Shabab has been fighting Somalia's central government for years to establish its own rule based on its strict interpretation of Islam's sharia law.
The group frequently carries out bombings and gun assaults in Somalia and elsewhere in its war against the Somalia military and the African Union-mandated AMISOM force that helps defend the central government.
Australian Associated Press