Updated

MOGADISHU, Somalia -- Heavy fighting erupted Thursday in Somalia's capital as African Union peacekeepers launched an offensive aimed at protecting famine relief efforts from attacks by Al Qaeda-linked militants, officials said. At least six people died.

Al-Shabab, Somalia's dominant militant group, has sent 300 reinforcement fighters to Mogadishu in recent days, said Lt. Col. Paddy Ankunda, spokesman for the African Union peacekeeping force.

Ankunda said the AU force believes that al-Shabab is trying to prevent aid from reaching the tens of thousands of famine refugees who have arrived in Mogadishu this month.

The al-Shabab militants already have killed men who tried to escape the famine with their families, saying it is better to starve than accept help from the West. The World Food Program says it cannot reach 2.2 million people in need of aid in the militant-controlled areas in southern Somalia because of insecurity.

Ankunda, a spokesman for the AU peacekeeping force in Somalia, said that AU forces had conducted a "short tactical offensive operation" Thursday in Mogadishu.

"This action will further increase security ... and ensure that aid agencies can continue to operate to get vital supplies to internally displaced," Ankunda said in a statement.

"We are concerned about the extremists' reckless attacks given the humanitarian activities being carried out presently," he said.

Ankunda said al-Shabab's decision last week to rescind permission allowing aid groups to operate in the areas the militants control already has denied hundreds of thousands of Somalis access to food aid.

He said the African Union Mission in Somalia, known as AMISOM, will keep humanitarian organizations informed of their future operations to limit the impact on the relief efforts.

"AMISOM fully understands the need to restrain military operations while the aid agencies mount their humanitarian campaign. However, we are here to maintain stability in Mogadishu, and if we perceive a threat from the extremist insurgents, then it is our duty to protect and defend the most vulnerable from this threat," he said.

Ali Muse, the head of Mogadishu's ambulance service, said his workers had collected six dead bodies and 20 wounded people.

A medical official at Mogadishu airport said wounded AU peacekeepers were to be evacuated by airplane to Nairobi, the capital city of neighboring Kenya, to be treated of injuries they sustained in the fighting. He spoke on condition of anonymity because he is not authorized to speak with the press. An Associated Press reporter watched as three wounded soldiers were put in a small jet for the flight.

Ankunda said he could confirm only that two AU troops had been wounded.

The devastating famine in the Horn of Africa threatens al-Shabab's hold on areas under its control, with the militants fearing that the disaster will drive away the people they tax and conscript into military service.

In the past, the militants have blocked aid workers from helping those in need in Somalia, fearing that foreign assistance would undermine their control.

A World Food Program plane with 10 tons of peanut-butter paste landed Wednesday in Mogadishu, the first of several planned airlifts in coming weeks.

In a statement Thursday, the WFP said that it has a funding shortfall of $252 million for the famine relief efforts in the Horn of Africa. The agency said it was encouraged by the response of some donor countries that have pledged $250 million to help.

The drought has created a triangle of hunger where the borders of Ethiopia, Kenya and Somalia meet. The U.N. believes tens of thousands already have died in Somalia in areas held by Al Qaeda-linked Islamist rebels.

WFP estimates more than 11.3 million people need aid across drought-hit regions in East Africa. The majority of those affected live in pastoral communities whose herds have been wiped out because of a lack of water.

But the famine has particularly ravaged Somalia because many aid groups were banned from militant-controlled areas in the south two years ago.

Somalia has been mired in conflict since 1991 when long time dictator Siad Barre was overthrown by warlords who then turned on each other. Islamist militants led by al-Shabab are attempting to overthrow the weak U.N.-backed government that is being propped up by about 9,000 AU peacekeepers from Uganda and Burundi.