Already in control of most of the capital, the AU force wants to advance through the Afgoye corridor – once a rural area to the north of Mogadishu but now home to hundreds of thousands of internally displaced people.
The corridor, believed to house the largest concentration of internally displaced people in the world, stretches some 30 km northwest of Mogadishu to the al Shabaab stronghold of Afgoye.
Captain Ndayiragije Come, the spokesman for Burundi’s contingent at the African Union Mission in Somalia (AMISOM), said their forces were now in part of Tre Disho village, 13 km from the capital.
“Our focus is to capture Afgoye and beyond but the time it will take depends on the resistance – we shall pursue al Shabaab everywhere we find them,” Come told Reuters.
“The main Mogadishu-Afgoye road is open now and functioning. We are now controlling part of Tre Disho – we chased al Shabaab but still a few of them are fighting us,” he added.
Al Shabaab has waged a bloody five-year campaign to topple Somalia’s Western-backed government and impose its harsh interpretation of Islamic law.
In what seemed to be preparation for an offensive in the Afgoye area, the African Union had told residents to stay away from the main roads.
The African Union has said that securing the Afgoye corridor would allow some 400,000 people, who have fled fighting in the capital in recent years, to get access to aid.
“We ask the population … to continue to stay in their places of residence, avoid unnecessary travel on main roads and not to stray far from their homes,” Lieutenant General Andrew Gutti, force commander of the AU forces, said in a statement.
Al Shabaab said they killed many soldiers in Tuesday’s fighting.
“We have killed about 30 soldiers. These are the government and Burundi troops who attacked us this morning” said Sheikh Abdiasis Abu Musab, the spokesman for al Shabaab’s military operations.
It was not possible to verify the casualty numbers.
“They are transporting their casualties with helicopters today. Fighting is still going on.” he added.
A Reuters witness at an airstrip in Mogadishu, from where the offensive was launched, said he saw two dead Somali soldiers as well as a wounded local TV reporter and two injured Burundian soldiers.
The witness saw helicopters taking off and landing and could hear gunshots around the airstrip. Residents in Tre Disho said they could hear gunshots from afar.
“We fear the fighting might spread towards our side,” said Farah Hassan, a resident of Tre Disho village.
“There are very few residents here. We see al Shabaab vehicles with anti-aircraft guns going to and from the gunshot direction.”
Al Shabaab rebels control swathes of central and southern Somalia but are being squeezed out of some areas by Kenyan and Ethiopian troops, which have launched incursions inside Somalia in support of the beleaguered government.
Somalia has been mired in chaos since warlords toppled dictator Mohamed Siad Barre in 1991.