The Somali capital Mogadishu is being wracked by the worst fighting in 15 years, with dozens killed and thousands fleeing the violence, aid agencies say.

Fighting resumed on Saturday for the third day, since Somali and Ethiopian troops launched an offensive against Islamist fighters.

Ethiopia said it had killed 200 "rebels" in the course of the operation.

But civilians said the city was being shelled indiscriminately, and that bodies were lying in the streets.

The International Committee of the Red Cross (ICRC) said the fighting was the heaviest in Mogadishu in 15 years, since the aftermath of the overthrow of Siad Barre in 1991.

Since then the country has been torn by constant fighting. A rare six months of order imposed by the Islamists ended when they were ousted by Ethiopian troops in December.

One resident said that, despite the capital's violent past, he had never been forced to leave, until now.

"Today I'm fleeing because shells are hitting residential areas indiscriminately," said Mohamed Deq Abukar Aroni, carrying two mattresses on his head, while his children carried belongings in paper bags.

"I saw two of my neighbors get killed. I'm not going to stay here anymore," he told the Associated Press.

Helicopter hit

A doctor at Alhayat Hospital said the building had come under mortar fire, and two staff had been wounded.

"Since early this morning I have been hiding here from the mortar shells so I can't help rescue people. I urge the two sides to respect health facilities," Dr Mohamed Dhere told AP on Friday.

UN Secretary-General Ban Ki-moon appealed for an immediate end to the fighting, saying in a statement he was "particularly concerned about the use of air strikes and the introduction of tanks and heavy artillery into densely populated parts of the city".

Ethiopia's information ministry said 200 members of the Union of Islamic Courts had been killed in the two-day offensive, but there was no independent confirmation of this.

Witnesses described how two Ethiopian helicopters fired on a "rebel" stronghold on Friday, before one of them was hit by an anti-aircraft missile.

"Smoke billowed from the cabin and it turned towards the ocean," Swiss journalist Eugen Sorg told Reuters.

"It crashed at the south end of the airport runway."

A spokesman for Ugandan troops, in Somalia as part of an African Union (AU) peacekeeping force, said they had recovered the bodies of two crew.

'Terrorist links'

Some 1,700 Ugandan troops are in Mogadishu as the advance party of an 8,000-strong AU force, which is supposed to replace the Ethiopian troops as they gradually withdraw.

Somalia's Interim Prime Minister Mohammed Ali Ghedi said the operation would continue in order to restore stability to Mogadishu.

"There are some insurgents in the city who have links with international terrorists and are fighting against the government and the people of Somalia," Mr Ghedi told the BBC Network Africa from the Arab League summit.

He said plans for the national reconciliation conference in April were under way and they have invited moderate Islamic scholars to the conference.

Photo caption

Smoke rising on the horizon in Mogadishu