At least 13 civilians have been killed and as many as 40 wounded in fighting between Islamist insurgents and African Union peacekeepers in Somalia's capital, Mogadishu. As Derek Kilner reports from VOA's East Africa bureau in Nairobi, the fighting was sparked when Islamists attacked the peacekeepers' base in the south of the city on Tuesday evening.
Ugandan peacekeepers responded to the attack with heavy weapons and tanks. Residents described shells falling on residential areas of Mogadishu, and many people fled the city on Wednesday.

A spokesman for the African Union peacekeeping force, Barigye Bahoku, said there had been no casualties among its troops. He rejected accusations that peacekeepers fired on civilian areas.

"The only firepower we ever exercise is to defend ourselves from our defensive position," Bahoku said. "We have not moved out, attacked any areas where the opposition forces are based. And yet we know where they are, but we will not move anywhere to attack them because that one does not fall within our mandate."

The fighting follows clashes on Monday that killed some 30 people in the city's main market area. Some analysts say the attacks may mark an increased effort by the insurgents to target the peacekeeping mission, in an effort to discourage further foreign intervention.

Around 2,500 African Union peacekeepers from Uganda and Burundi are currently in Somalia, far less than the 8,000 approved for the mission. They have had little success in stemming the conflict between various Islamist-led militias on the one hand, and Ethiopian troops backing the country's transitional government on the other.

The regional body wants the United Nations to take over peacekeeping operations, but the U.N. is unlikely to take up the request without a considerable improvement in the security situation, for fear of being bogged down in a messy conflict.

Zacharia Mohamed Abdi, a spokesman for a hard-line faction of the Alliance for the Reliberation of Somalia, an Islamist opposition group based in the Eritrean capital, Asmara, blamed Ugandan peacekeepers for attacking Somali civilians.

"AU forces actually have slaughtered the Somali people," Abdi said. "And this is yet another failure for the AU forces in Somalia, or anywhere indeed in Africa. I would appeal to president Museveni to pull out his forces from Somalia. This is an atrocity which has been going on for almost two years particularly by the Ethiopians who are invaders and occupiers."

The identity of those who attacked the peacekeepers has been difficult to determine. Much of the insurgent violence has been carried out by the radical Islamist Shabaab militia, which has been linked to al-Qaida. Other fighters pledge loyalty to Abdi's Asmara-based faction, led by Sheikh Hassan Dahir Aweys.

Another more moderate faction of the Alliance for the Reliberation of Somalia recently signed a peace agreement with transitional government in Djibouti. But it has had little effect on the fighting, and has been rejected by many in the opposition.

An estimated 9,000 civilians have been killed by fighting in Somalia since the latest insurgency began in early 2007, and some one million displaced, in what the U.N. has called Africa's worst humanitarian crisis.