-- The United Nations' top elections official, Carina Perelli, was fired Tuesday after complaints that she sexually harassed subordinates and presided over a department that permitted such abuses to flourish, senior U.N. officials said.

Perelli, 48, was notified by letter Tuesday morning that she was "summarily dismissed" without pay for engaging in "sexual and professional harassment" of her staff. U.N. officials changed the lock in her office, froze her e-mail account, and barred her from entering U.N. headquarters without permission and an escort.

The United Nations has never publicly detailed charges against the Uruguayan elections expert. But Stephane Dujarric, the world body's chief spokesman, said they include "allegations of harassment, including sexual harassment and abuse of authority." He said the United Nations feels "very strongly" about their veracity: "Otherwise, we wouldn't have gone ahead with the case."

In an interview, Perelli denied harassing her workers and vowed to challenge the decision through the United Nations' appeals process. "We're going to fight this one, we're going to appeal," Perelli said. She said her lawyers are also considering filing a lawsuit against the United Nations.

Perelli said that the United Nations has denied her due process and that the allegations -- which are contained in a confidential report by the organization's personnel department -- are vague and unsubstantiated. Perelli said that no staff member filed a formal harassment complaint against her and that the United Nations has never conducted a formal investigation to test whether the allegations are true.

The timing of the decision was criticized by John R. Bolton, the U.S. ambassador to the United Nations, who said nothing should be done to disrupt Iraq's Dec. 15 election. "Why make a decision 10 days before the election in Iraq?" Bolton asked. "If you're going to make a decision, make it at an appropriate point."

Perelli has been lauded for her work at the United Nations, overseeing successful elections in Afghanistan, Iraq and the Palestinian territories. President Bush has singled out Perelli for her role in preparing Iraq's elections.

Some members of the Iraq election unit are "in disarray right now," Perelli said. "I hope that they can pull through it. I'm going to be cheering for them. But, obviously, the timing [of the dismissal] is not the best suited to contribute to their work."

Dujarric said that the action will not affect Iraq's election. He said that another U.N. electoral official, Craig Jenness of Canada, has been overseeing the organization's role since Oct. 23. "He is the lead person for the U.N. on the Iraqi elections," Dujarric said.

Perelli's management of the elections unit came under scrutiny a year ago, when employees complained of management flaws. A review, carried out by a Swiss consulting firm, found that employees were subjected to unwanted sexual advances and that "a constant sexual innuendo is part of the fabric" of daily life.

The report led to an internal review by the U.N. personnel department. That review, which elicited additional allegations of sexual misconduct, was cited by officials in taking Tuesday's action.

Carina Perelli is escorted out of the organization's headquarters after being fired as the top U.N. elections official.