African Union troops and Somali forces seized the formerly Islamist-held town of Jowhar Sunday, wresting control of one of the largest remaining towns held by the Al-Qaeda linked Shebab, officials said.

"We took control this morning and are now establishing security in Jowhar," Colonel Ali Houmed, a spokesman for the African Union Mission in Somalia (AMISOM), told AFP.

"AMISOM troops alongside Somali National Forces entered the town, there was little fighting as the Shebab largely fled ahead of us."

Shebab spokesman Abdiaziz Abu Musab confirmed to AFP that the extremist forces had pulled out of the town, which lies some 90 kilometres (55 miles) north on a key road from the capital Mogadishu.

"We have withdrawn our troops from Jowhar for strategic reasons," Abu Musab said, adding that the forces had pulled out without suffering any casualties and remained "close by" to the town.

"We will hunt the invaders from inside and outside Jowhar," he added.

The loss of Jowhar is a significant blow to the Shebab, who have lost a string of towns in recent months to the 17,000-strong AMISOM force, as well as to Ethiopian troops who invaded Somalia last year from the west.

AU troops are also battling to open up the road northwest from Mogadishu to link the capital with Baidoa, which is held by Ethiopian troops.

Kenyan troops -- who invaded Somalia a year ago before later integrating into AMISOM -- have also pushed up from the south, and seized the Shebab bastion and major port of Kismayo in September.

The hardline insurgents still control the small port town of Barawe, lying some 180 kilometres down the coast from the capital.

The fighters have largely retreated ahead of each assault, with some reportedly relocating to the northern Galgala mountains in Somalia's semi-autonomous Puntland region.

But the Shebab remain a potent threat, still controlling rural areas as well as carrying out guerrilla attacks -- including suicide bombings -- in areas apparently under government control.