"What happened this week is terrible and should be condemned ... but it is not new. It has been going on for 18 years," U.N. envoy to Somalia, Ahmedou Ould-Abdallah, told Reuters.

About 100 people died in fighting last weekend between allied Ethiopian-Somali troops and Islamist insurgents.

And in an incident inflaming passions on all sides, beheaded corpses lay outside a Mogadishu mosque where Ethiopian soldiers were accused of killing about 20 people, including an imam and Koranic students. Addis Ababa has denied that as "lies".

Ould-Abdallah, a Mauritanian with one of the toughest jobs in international diplomacy, is trying to bring representatives of Somalia's government and exiled opposition group together at a low-profile meeting in Djibouti on May 10.

"I am trying to tell the Somalis they should meet at a very technical level to have a minimum political understanding. Instead of running from one (foreign) capital to another, they must talk to each other," he said at his Nairobi office.

Hardline Islamists, who have waged an insurgency since early 2007, are refusing to join peace talks until Ethiopian troops have left. And some moderate Islamist leaders, who had said they would support talks, are doubtful after the latest violence.

But Ould-Abdallah indicated he would be flexible on the timetable, saying that starting the process was more important than being fixated on a particular date.

INTERNATIONAL "ABANDONMENT"

The Horn of Africa nation of nine million people has suffered constant violence since the 1991 fall of a military dictator. Ethiopia sent thousands of troops in 2006 to help the Western-backed interim government oust Islamists from Mogadishu.

Saying it was impossible to verify facts on the ground without a permanent U.N. presence, Ould-Abdallah called for the world body's mainly Kenyan-based offices dealing with Somalia to be moved into the country, with proper security.

"We cannot, for 18 years, be sitting in Nairobi and say we will work on Somalia ... by remote control," he said.

"Either we move closer to the victims of abuse, of violence, of drought, of famine ... Or we give up on Somalia and devote these resources to other places."

The envoy saw little prospect of a U.N. peacekeeping force in Somalia until there was internal political progress.

"This will not happen if we don't have a group of Somalis who have the courage to sit together and make that minimum agreement," he said. "The U.N. has so many things on its plate. They are requested and welcome in many other places, so I don't see them rushing to Somalia unless there is minimum stability."

A small 1,800-strong African Union force, mainly Ugandans, has done little to stem violence in Somalia, though it has won plaudits for providing medical care and securing areas like Mogadishu's port and presidential palace.

Ould-Abdallah said the awkward truth was that some Somali leaders were "comfortable" with perpetuating war for selfish motives, despite the immense suffering to the population.

He criticised the international community for its "neglect, terrible abandonment" of Somalia, particularly on failing to pursue justice for war crimes as it had done in places like Ivory Coast, Cambodia or former Yugoslavia.

"I have not seen anyone put on the blacklist ... or sanctions against criminals and their foreign associates, people sending weapons," he said.