MOGADISHU, Somalia - Civilians were caught in the crossfire Wednesday as the government's Ethiopian backers used tanks and heavy artillery to pound insurgent strongholds, witnesses said.

Ethiopian military officials met with elders of Mogadishu's dominant clan to try to broker a peace, said Abdullahi Sheik Hassan, a spokesman with Mogadishu's powerful Hawiye clan. He gave no further details. Hundreds have been killed in eight straight days of fighting.

An extremist Islamic group claimed responsibility for car bomb attacks Tuesday against Ethiopian troops and a hotel housing lawmakers loyal to Somalia's interim government. Known as the Young Mujahedeen Movement, it said in a statement posted on the Internet that a Kenyan called Othman Otayo carried out a suicide attack against the Ethiopian military base. The authenticity of the statement could not be confirmed.

The group is part of the extremist Shabab movement, whose leader Aden Hashi Ayro was recently chosen as head of Somalia's al Qaeda cell and was one of the people targeted by a U.S. airstrike in January in Somalia.

The continued fighting comes despite UN Secretary General Ban Ki-moon calling on warring sides to end the violence and allow humanitarian assistance to reach the needy. The Somali government and its Ethiopian allies are trying to quash a growing Islamic insurgency but civilians are getting caught in the crossfire.

The UN says more than 320,000 of Mogadishu's 2 million residents have fled since February, sending streams of people into squalid camps with little to eat, no shelter and disease spreading. The war-ravaged country is suffering its worst humanitarian crisis in its recent history, according to the UN.

Ethiopian Prime Minister Meles Zenawi told journalists late Tuesday that he believed the exodus and the death toll had been exaggerated.

"I have been stuck inside for the last three days and have no food left," mother of nine, Hawa Mualim told The Associated Press by telephone, saying there was fighting outside her house in northern Mogadishu and she was too scared to venture outside.

Somali government troops are being used to flush out insurgents from the tiny alleyways and small houses as Ethiopian tanks and artillery pound positions, resident Osman Ali Yusuf said from the Tawfiq area in south of the city where fighting was also taking place.

"Ethiopian troops have taken control now," he said.

Human rights groups say more than 350 people have been killed in the last eight days, the majority civilians. The last bid to wipe out the insurgency left more than a 1,000 dead, said local rights groups and traditional elders.

Western and UN diplomats fear Somalia's government is holding up vital aid supplies to people fleeing fighting. The government has been demanding to inspect all food and medical shipments, holding up potentially lifesaving aid, European and American officials warned in letters obtained Tuesday by The Associated Press.

UN humanitarian chief John Holmes told reporters that representatives of his office and other UN agencies met in the southern town of Baidoa on Monday with a newly established Inter-Ministerial Committee set up by the transitional government to discuss the lack of humanitarian access and the lack of cooperation from the government.

At the meeting, Holmes said, "they have assured us of full support for humanitarian access and humanitarian workers," including to all airstrips, which he welcomed but cautiously.

"The reassurances we received yesterday were good as far as they go, but they have to be translated into action," he said.

Somalia has not had an effective national government since 1991, when warlords overthrew dictator Mohamed Siad Barre and then turned on one another, throwing the country into anarchy. The current administration was formed in 2004 but has struggled to extend its control over the country.

The insurgents are linked to the Council of Islamic Courts, a hard-line religious movement that had controlled Mogadishu and much of southern Somalia for six quiet months in 2006. Somali and Ethiopian troops drove the group from power over the New Year. The militants reject any secular government, and vow to fight until Somalia becomes an Islamic state.