Gunmen walk through a crowd of people in Mogadishu (file photo)

At least 13 people have been killed Saturday in Somalia's capital, where new fighting has broken out between rival factions.

Witnesses say Islamic militias and fighters for a coalition of warlords have been pounding each other with machine-gun and artillery fire.

The fighting is centered in Mogadishu's northern Galgalato district and southern Daynile district.

This is the fourth round of fighting between the sides this year as they battle for dominance in the city.

At least 60 people have died in the latest clashes, which began on Wednesday. The Islamic militias have reportedly seized a key road junction and hotel during the battles this week.

The violence shattered a tenuous ceasefire that was established on May 14. At least 260 people in all have died since the fighting in Mogadishu erupted in February.

Somalia has been without an effective central government since rebels overthrew dictator Mohamed Siad Barre in 1991. A U.N.-backed transitional government based in the city of Baidoa has been unable to establish control.

The coalition of secular warlords, called the Alliance for the Restoration of Peace and Counter-terrorism, accuses the city's Islamic authorities of providing a safe haven for al-Qaida terrorists.

The Islamic authorities deny this and accuse the warlords of receiving support from the United States - a charge Washington has refused to either confirm or deny.

Some information for this report was provided by AFP and Reuters.