The clashes started late Sunday and continued Monday morning, the Elman Peace and Human Rights Organization said.

"These casualties are from the overnight shelling. We are still monitoring Monday's casualties. The shelling was terrible," said Ali Yasin Gedi, Elman's vice chairman.

Residents said government shells targeted houses occupied by Islamist al Shabaab rebels in the north of Mogadishu. Washington says the group is al Qaeda's proxy in the region.

"We saw al Shabaab carrying their dead and injured in a minibus. But we do not know the exact figure of the deaths," Hassan Nur, a resident, told Reuters.

"The government shells almost leveled houses that housed local and foreign al Shabaab people."

Government and al Shabaab officials could not be immediately reached for comment.

Somalia has not had an effective central government for close to two decades and the international community and neighboring countries are worried about the threat posed by al Shabaab insurgents now controlling a large part of the country and fighting its fragile government.

The near-daily clashes have killed at least 21,000 people since the start of 2007.

For weeks, the government has been promising to launch an offensive against al Shabaab and another rebel group, Hizbul Islam, which both want to impose a harsh version of sharia law.

A government official who wanted to remain anonymous told Reuters the pro-government Ahlu Sunna Waljamaca militia was meeting a government delegation in neighboring Addis Ababa.

"Currently the talks are continuing. We're discussing with Ahlu Sunna Waljamaca on how best we can accommodate them both politically and militarily. If it goes well at this first stage, then we will focus on uniting forces to face on war," he said.

(Additional reporting by Ibrahim Mohamed and Abdiaziz Hassan; Editing by Giles Elgood)

Source: Reuters