Baghdad, Iraq ? The death toll among coalition forces rose Saturday when three British soldiers were killed in a guerrilla attack in southern Iraq. Also, U.S. troops killed two Iraqi Turkomen who opened fire when soldiers arrived to quell a bloody ethnic clash in the north.

Despite continuing violence, sabotage and terror attacks — including this week’s suicide bombing of U.N. headquarters — the American administrator for Iraq said the U.S.-led coalition would not slow efforts to rebuild the country, shattered by war and 13 years of U.N. sanctions.

“We have never hidden the fact that we have security problems in Iraq,” L. Paul Bremer told a news conference.

Also in Baghdad, U.N. workers who had not left Iraq after Tuesday’s attack resumed work in a cluster of tents set up at the battered Canal Hotel compound, former home of U.N. offices.

Investigators and soldiers searched piles of debris for human remains and clues in the truck bombing that killed at least 23 people, including top U.N. envoy Sergio Vieira de Mello, whose memorial was held Saturday in his native Brazil.

One of the envoy’s dying wishes was for the United Nations to remain in Iraq and continue work to establish democracy, U.N. Secretary-General Kofi Annan told mourners.

“Let us respect that,” Annan said. “Let Sergio, who has given his life in that cause, find a fitting memorial in a free and sovereign Iraq.”