Fighting between rival armed opposition groups has killed at least 13 people in central Somalia, residents say.

Members of the Ahlu Sunna Wal-jama'ah group clashed with rivals from the al-Shabab movement outside the town of Wabho, north of Mogadishu, the Somali capital, in fighting that began on Saturday.

"Thirteen people are dead - eight of them combatants, from both sides - and seven others were injured," Abdisamed Adan Yusuf, a local resident told the AFP news agency.

The fighting continued on the outskirts of the town on Sunday, residents said.

Ahlu Sunna Wal-jama'ah said its fighters had captured seven al-Shabab members.

"We lost one and four others were injured from our side," Sheikh Abdullahi Sheikh Abu Yusuf, a spokesman for the Ahlu Sunna, told the Reuters news agency.

"We shall conclude the war in a short while," he said. "Wabho is now in our hand and we are now about to capture El Bur, their biggest base."

There was no immediate comment from al-Shabab.

Sharia-based law

The two groups have clashed repeatedly over control of the region.

Al-Shabab and allied groups control much of southern and central Somalia and want to impose their version of sharia, or Islamic law, in the country.

Earlier this month, Somalia's cabinet voted to make Islamic law the basis for the country's legal system in an attempt to isolate more extreme armed groups by agreeing to a demand supported by much of the Somali population.

The bill must still be approved by parliament.