Words like "massacre," "horrific" and "appalling" have been employed to describe the situation there, amid widely differing estimates of the casualty numbers and property damage after Israeli bulldozers were reported to have leveled dwellings.

Israel agreed to the dispatch of the UN mission. Its foreign minister, Shimon Peres, said during a Washington visit this past week-end that Israeli troops were under orders not to harm civilians at the camp.

Israel has claimed that Jenin, home to about 15,000 impoverished Palestinians, was a hotbed for terrorism.

Terje Roed-Larsen, the UN special coordinator in the Middle East and one of the first to see the damage, has been getting flak for speaking out about the Jenin affair. Annan leapt to his defense Monday, voicing confidence in his man's judgment.

The UN Relief and Works Agency for Palestinian refugees has long had difficult relations with Israel, but Peres called Annan to say UN fact-finding would be OK. After announcing his choice of Ahtisaari, the Secretary General told reporters the Israelis had promised to cooperate with anyone he sent in to find out what happened at Jenin and said that they "had nothing to hide."

As for himself, he withheld judgment until the mission had done its work. "We would want to get the facts as quickly as possible," Annan said.

A top grade UN bureaucrat before he entered politics, Ahtisaari ran the highly successful UN operation that brought the former South African territory of South West Africa to independence, as Namibia. Since he ceased being a head of state, he has undertaken troubleshooting assignments in the Balkans and elsewhere and has shown a willingness to pick up the ball and run with it whenever the UN or the European Union, of which Finland is a member, sought an assist and decided he was the man to supply it.

Other members of the fact-finding team are top-flight in their own right: Sadako Ogata of Japan, former UN High Commissioner for Refugees; Cornelio Sommaruga of Switzerland, former president of the International Committee of the Red Cross; General Bill Nash of the US, who will serve as military adviser, and Thomas P. Fitzgerald of Ireland, designated to be the police adviser. Thus, all of the team are nationals of developed countries, which is somewhat unusual. Then, this is an unusual problem they have to tackle and Annan surely wanted the least possible risk of seeing the investigation take an unwelcome political turn.

Mounting a UN peacekeping force is a long, tedious business, but this mission is already straining at the leash. It will start work "without delay," Annan said. "It will first assemble in Europe this week and then travel to the region as quickly as possible." Pending the members' assessment of the situation in the camp, he could not guess how long the mission will be at work or when its report will be ready.

This will go to him first, and then to the Security Council.

The Secretary General emphasized the need for both the Israeli government and the Palestinian Authority to cooperate fully and provide full and complete access to all sites, sources of information and individuals the team members might want to interview.

Ahtisaari, who accompanied Annan for the announcement, wisely kept his counsel, saying only that the group would "go after all the necessary information."