Officials say African Union and Somali government troops have seized positions from militant group al-Shabab in the capital, Mogadishu.

The AU force, known as AMISOM, said Friday that it had driven al-Shabab fighters from Mogadishu University and the Barakat Cemetery, areas on the city's northern outskirts.

Witnesses in the area reported hearing heavy gunfire around dawn Friday. Reports from the area say at least three government soldiers were killed when their vehicle was attacked.

Al-Shabab abandoned most of the city in August but had held on to a few areas and has continued to carry out bombings and guerilla-style attacks in the war-torn capital.

The militant group is fighting to overthrow Somalia's U.N.-backed transitional government and impose strict Islamic law. It is battling AU forces in Mogadishu, as well as Kenyan soldiers in the south and Ethiopian troops in the west.

Mogadishu has seen near daily attacks by insurgents in recent days. On Thursday, a bomb exploded near a crowded area of makeshift shelters for refugees. The blast, which appeared to target a police checkpoint, killed six people.

The violence comes as Somalia on Friday marks six months since the United Nations first declared a famine in six regions of southern Somalia.

Although famine warnings have now been lifted in three of those regions, humanitarian groups say millions are still in urgent need of food aid.

But several humanitarian agencies have been forced to suspend aid to the region because of the violence.

On Thursday, Doctors Without Borders announced it was closing its two largest medical centers in Mogadishu after two of its workers were killed last month.

Last week, the International Committee of the Red Cross suspended aid to 1.1 million Somalis, saying that local authorities linked to al-Shabab had blocked aid to several regions.

The Islamist militant group has banned most foreign aid groups from operating in areas under its control.