Mogadishu  - Clashes broke out between two allied Islamist insurgent groups in the Somali port town of Kismayo Thursday, residents of the town said.

Al-Shabaab and Hizbul Islam have been working together to try and topple the fragile Western-backed government and between them they control much of south and central Somalia.

However, residents of Kismayo told German Press Agency that three people had died in clashes between the groups, which began early on Thursday and were still ongoing.

The reason for the battle was unclear.

Somalia is widely regarded as a failed state, and has been embroiled in chaos since the 1991 ouster of dictator Mohamed Siad Barre and descended further into lawlessness in early 2007, when the insurgency kicked off following an Ethiopian invasion.

More than 18,000 people have died since the insurgency began. Over half of the Somali population is now dependent on food aid due to the conflict and drought. (dpa)