The United Nations said the decision to relocate 600 people - nearly half of its international staff - should not be seen as a diplomatic retreat. But the move comes amid concerns that Taliban fighters have been emboldened by the attack and may try to strike again.

"They realize that if they hit the United Nations again, there's a serious risk of the United Nations leaving the country," said one diplomat in Kabul, who spoke on the condition of anonymity so that he could speak candidly about the U.N. plans.

One of the biggest worries is that insurgents in Afghanistan are trying to duplicate the strategy of Iraqi extremists who forced the United Nations to shutter its Iraqi operations in 2003 after a devastating truck bomb hit the U.N. headquarters, killing 22 people, including the top U.N. official in the country.

If the United Nations were to pull out of Afghanistan, it would force all other international aid groups to rethink their work in the country and undermine President Hamid Karzai's shaky government.

"That's the name of the game: Get the U.N. out," the diplomat said. "If they can get the United Nations out, then they think they can take out the Karzai government."

Kai Eide, the Norwegian diplomat who heads the U.N. mission in Afghanistan, said there were no plans to abandon the country. "We are not talking about pulling out," he said at a news conference in Kabul. Instead, he said, the United Nations is going to relocate hundreds of international workers while it figures out how to protect the staff better.

But he made clear the United Nations is deeply concerned about the deteriorating situation and the failure of Karzai's government to stamp out corruption.

"There is a belief among some that the international commitment to Afghanistan will continue whatever happens because of the strategic importance of Afghanistan," he said. "I would like to emphasize that that is not correct. It is the public opinion in donor countries and in troop-contributing countries that decides on the strength of that commitment."

The United Nations has about 1,100 international staff members in Afghanistan. The roughly 600 nonessential staff will be relocated temporarily to other parts of Afghanistan or to nearby regional offices, said Aleem Siddique, a spokesman for the U.N. operation in Afghanistan.

Currently, much of the staff lives in a well-known network of guesthouses - small, lightly guarded compounds - spread out across Kabul. Last week, three extremists wearing Afghan police uniforms exploited the vulnerability of the guesthouses by scaling the walls of one compound and staging an attack that killed five U.N. workers, two Afghan security guards, and the relative of an Afghan politician.

Afghan officials said six men had been arrested for the attack.

Over the next four to six weeks, Siddique said, the United Nations will search for ways to consolidate its housing to reduce danger. Along with its international staff, the United Nations has about 4,000 Afghan employees who will continue their work, he said.

The United Nations is facing increasing dangers in the region, which make it more difficult for its staff to work in the area. Last week, the United Nations decided to pull its international staff out of northwestern Pakistan. A suicide bomber struck a U.N. office last month in Islamabad, killing five people who worked for the World Food Program.

The U.N. decision in Kabul came on the same day that a NATO strike in southern Afghanistan reportedly killed as many as 11 civilians and sparked local protests.

In a statement yesterday, NATO said that its forces had fired a rocket at a group of nine people thought to be concealing an improvised bomb in a village in Helmand province and that the troops did not know of any civilians in the area. NATO said it was looking into the allegations.