By Mohamed Ahmed
MOGADISHU (Reuters) - Somalia offered an amnesty to militants still fighting in the capital Mogadishu Tuesday, three days after the country's president declared victory over the insurgent al Shabaab group, which has withdrawn most of its combatants from the city.
It was the first time the interim government, which has struggled to quash a four-year Islamist rebellion, had offered immunity to al Shabaab fighters.
"The Transitional Federal Government of Somalia has offered a general amnesty to insurgent fighters remaining in Mogadishu who give themselves up and renounce violence," the government said in a statement.
Some experts say al Shabaab's pull-out merely extends the government's hold on the capital by a few districts, but will do little to bring tangible peace to the rest of the anarchic country and may herald a new wave of al Qaeda-inspired attacks.
The 9,000-strong African Union peacekeeping force, known as AMISOM, urged the deployment of an additional 3,000 troops to help it secure the neighborhoods vacated by al Shabaab.
The United Nations has authorized a taskforce of up to 12,000 soldiers.
"The Mogadishu area is too large for our present troops to secure properly -- there will be some gaps," Lieutenant-Colonel Paddy Ankunda, AMISOM's spokesman, told Reuters.
A Western diplomat said the militants' withdrawal had caught the Somali government and peacekeepers off-guard and warned it was a question of when, not if, al Shabaab returned to Mogadishu.
"It's only a question of time before we see them back in a different form," said the diplomat, declining to be named.
There were fears warlords could step into the void left by al Shabaab's departure.
"However, if the TFG overplays its hand and tries to assert a hegemony in the vacuum left by the retreating militants, it risks provoking a very strong reaction by clans and local communities ... to which it has never provided any services," said J Peter Pham, director of the Atlantic Council think-tank.
The amnesty did not appear to extend to al Shabaab fighters outside the capital. The al Qaeda-affiliated militants control much of southern Somalia where 2.8 million people face starvation because of drought and conflict.
Al Shabaab called its retreat from Mogadishu tactical and said its bloody struggle to topple the Western-backed government would continue.
Monday afternoon, a suicide car bomb heading for the rubble-strewn capital detonated prematurely 13 km (8 miles) south of Mogadishu.
Gun battles raged overnight in at least two northern districts of Mogadishu and residents said government forces and al Shabaab also traded volleys of mortar rounds.
Mohamed Abdullah, who lives in Mogadishu's Hosh neighborhood, said the militants, who want to impose a strict interpretation of Sharia law on the famine-stricken population, launched an assault on two government military bases.
"We weren't expecting such attacks from al Shabaab now. Clearly the group is still present and still have some power," Abdullah told Reuters.
President Sheikh Sharif Ahmed arrived in Tanzania Tuesday and was expected to hold talks with President Jakaya Kikwete.
There were no details on what they would discuss but Ahmed has already visited Uganda and Djibouti to encourage the delivering of aid within Somalia to stem the exodus of refugees to Kenya and Ethiopia.
Asked whether al Shabaab's exit might hasten the flow of aid to the area, the U.N. refugee agency (UNHCR) said Mogadishu remained volatile.
"You have a vacuum in the (Shabaab) areas, and you have competing armed groups who work for their own profit. You have even competing militias in different parts of the town," UNHCR spokesman Andrej Mahecic told a media conference in Geneva.
(Additional reporting by Abdi Sheikh, Richard Lough in Nairobi and Tom Miles in Geneva; Writing by Richard Lough; Editing by James Macharia)