Mogadishu - Over 20 people died in Somalia during fighting between Islamist insurgents and government forces Wednesday, including a dozen leaving evening prayers, witnesses said Thursday.

The stray shell that devastated a mosque in north Mogadishu late Wednesday evening was the worst single incident in a day of heavy clashes in north and south Mogadishu, where insurgent groups al-Shabaab and Hizbul Islam are trying to oust President Sheikh Sharif Sheikh Ahmed.

Mogadishu's police chief, Colonel Ali Saed, was amongst those killed earlier in the day as government forces attempted to dislodge the insurgents, who gained territory when they began a major offensive in early May.

Dahir Dhere, deputy director of Medina Hospital, told the German Press Agency dpa that several dozen people were treated at the hospital, some of them for serious injuries.

The latest round of fighting has claimed the lives of around 300 civilians and has sent over 120,000 fleeing Mogadishu since early May.

Somalia has been embroiled in chaos since the 1991 ouster of dictator Mohamed Siad Barre.

The UN-backed appointment of Sheikh Sharif, a former insurgent ally, briefly raised hopes of peace, but the insurgents say he is too close to the West.

The insurgency began in early 2007 after Ethiopian forces invaded to oust the Islamic Courts Union, a group headed up by Sheikh Sharif and other prominent Islamists.

An estimated 18,000 civilians have been killed in the insurgency, while over a million have fled.

The insurgency, combined with drought, has left millions of Somalis dependent on food aid and has allowed piracy to flourish off the coast of the Horn of Africa nation. (dpa)