An exchange of mortar shells between Somali government forces and Islamist insurgents killed at least nine civilians and injured 14 others, a human rights group said on Monday.

The clashes started late on Sunday and continued on Monday morning, the Elman Peace and Human Rights Organisation 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 in the north of the city used by hardline al Shabaab rebels, who this month declared their loyalty to al Qaeda.

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

"The government shells almost levelled 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 neighbouring 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.

In Tokyo on Monday, Somali Foreign Minister Ahmed Jama Jangeli told reporters the assault was imminent.

"We have left the decision to the military commanders on the ground. They needed more time, but their preparations are almost complete and they are the ones who will determine the date for those operations," he told a news conference.

"We want to do it right. The appropriate time would be determined by the military commanders, but I believe it will be very soon, very very soon when these operations will be taken."

A government official who wanted to remain anonymous told Reuters the pro-government Ahlu Sunna Waljamaca militia was meeting a government delegation in neighbouring 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 in Mogadishu, Abdiaziz Hassan in Nairobi and Isabel Reynolds in Tokyo; Editing by Dominic Evans) 

Source: Reuters - By Abdi Sheikh and Abdi Guled