|Somali forces have reinforced their hold on Mogadishu, but al-Shabab called its retreat a "tactical move" [AFP]
Somalia's government has offered an open amnesty to al-Shabab fighters after the rebels made a surprise withdrawal from the capital, Mogadishu, over the weekend.
"We offer an amnesty - put down your weapons and your guns, and come and join the people and your society," Abdirahman Osman, a government spokesman, was quoted as saying by the AFP news agency on Tuesday.
"For those who have been misled by the senior commanders, now is the time to end the war," he said.
Al-Shabab, who still govern over much of southern Somalia, have waged a bloody war since 2007 to topple the Western-backed transitional government.
The fighters, who had controlled around half of Mogadishu, abandoned their positions on Saturday but some units remained active within the capital.
Government officials celebrated the pullout by the rebels but the fighters said it was merely "a change of military tactics."
Troops thinly stretched
This vacuum has left the city largely to be taken over by the African Union [AU] troops.
Al Jazeera's Peter Greste, reporting from Mogadishu, said the AU troops appear to be thinly stretched across the region.
"They are now not just controlling a frontline that cuts through the city, they have control of the entire city. So that means the physical area they have to man has doubled," he said.
"This is a very different job from the one they were fighting - a front line offensive is a relatively straight forward military operation particularly compared to the counter-insurgency one that they are trying to run.
"Keeping control and keeping security is a very, very difficult job indeed. They are requesting 3,000 more troops. These are not additional numbers, but rather part of the 12,000 that was initially mandated and promised to them but have simply not arrived."
An AU official told Al Jazeera that "these additional troops were absolutely essential, especially if the international community wanted to maintain stability and get aid out".
Meanwhile, fighting was reported as rebel remnants clashed with AU-backed government troops following the pullout.
Sporadic gunfire was heard in the city on Tuesday morning, according to AFP.
The 9,000-strong AU force (AMISOM) and government troops have meanwhile reinforced their hold over former al-Shabab positions in an effort to allow more aid into the famine-struck capital.
"The extremists have been preventing the provision of food to hungry Somalis and this has opened up the opportunity to help many more people," Boubacar Gaoussou Diarra, the AU special representative to Somalia, said in a statement released late on Monday.
AMISOM however warned people against returning to former al-Shabab-controlled areas of the "high possibility" of "roadside bombs and pockets of remaining extremist fighters," Diarra said.
The UN Coordination of Humanitarian Affairs (OCHA) said it was assessing how the group's withdrawal would open aid group access to the war-torn city, which about 100,000 people have fled from in the past two months to escape extreme drought.
"Although it is too early to know what the impact on the overall situation is, humanitarian actors are assessing the ability to operate and/or scale up activities," it said in a statement on Tuesday.
The United Nations has officially declared famine in Somalia for the first time this century, including in Mogadishu and four southern Somali regions.
"Famine... is expected to spread across all regions of the south in the coming four to six weeks," OCHA warned. "Cases of acute watery diarrhoea are increasing across Somalia," it added.
The UN's food monitoring unit has described Somalia as facing the most severe humanitarian crisis in the world and Africa's worst food security crisis since the country's 1991-1992 famine.
Parts of Ethiopia, Djibouti, Kenya and Uganda have also been hit by the Horn of Africa's worst drought in decades.