Mogadishu - Somali insurgent group al-Shabaab has taken over the port town of Merka, 90 kilometres southwest of the capital Mogadishu, after government forces abandoned their posts overnight, residents said Wednesday.

"Heavily armed Islamists entered Merka without any resistance," Aweys Dahir, a resident in Merka, told Deutsche Presse-Agentur dpa by telephone. "They have already set up two bases in town and are patrolling the streets."

The fighters also took over two other towns in the region.

Insurgents have been fighting Somalia's transitional federal government since Ethiopian troops helped oust the Union of Islamic Courts in early 2007.

They have slowly begun to regain ground, and in August this year took over the key port town of Kismayo.

As the insurgents take over more territory, human rights activists are concerned that stringent punishments will be handed out under the rebels' interpretation of Islamic law.

Fears were raised by a recent case in Kismayo, when a 13-year-old girl was stoned to death for adultery.

United Nations children's agency UNICEF said the girl was in fact raped by three men while walking to visit her grandmother in the capital Mogadishu.

Civilians have suffered horrendously during the fighting, often finding themselves caught in the crossfire.

An estimated 10,000 civilians have died since the insurgency began and almost a million have fled their homes, many from Mogadishu.

The Horn of Africa nation has been plagued by chaos and civil war since the ouster of dictator Mohamed Siad Barre in 1991. (dpa)