UNITED NATIONS - The annual meeting of the UN's most important human rights watchdog was disrupted after a Cuban diplomat sucker-punched a leading anti-Castro campaigner inside the world body's Geneva headquarters, knocking him out cold.

For years, leading human rights groups have criticized the UN Human Rights Commission, saying countries with some of the worst records of abuse have been elected to it to help one another avoid international censure. This year has been no different.

The commission has seen rejection of censures against Russia, China and Zimbabwe, and the repeated postponement of a measure criticizing Sudan, where UN officials have accused the country's Arab rulers of waging genocide against black-skinned Sudanese.

But the six-week meeting, which wraps up today, took on an air of tragic farce with the assault on Frank Calzon, executive director of the Washington-based Center for a Free Cuba.

The attack occurred as delegates poured out of the main commission hall after a ballot on Cuba's human rights record, which Cuba lost by just one vote.

Mr. Calzon was preparing for a live interview with a reporter from Radio Marti, the U.S.-sponsored network that broadcasts to Cuba, when the Cuban delegate jumped off an escalator behind him and punched him in the side of the head, witnesses said.

UN security officials had to move in to prevent other Cuban delegates from joining the fray, with one pulling out a can of Mace.

"This type of behaviour is not just a breach of diplomatic protocol, but is itself a human rights violation," said Jennifer Windsor, executive director of Freedom House, a New York-based democracy-monitoring group, whose Cuba project Mr. Calzon directed for a decade.

"A brutal attack inside the very building where the Commission on Human Rights meets only underscores the deep crisis the commission finds itself in today."

A senior U.S. delegate helped seize the attacker, but UN security services released him after Cuba claimed diplomatic immunity from prosecution.

A report on Cuba's government-controlled radio in Havana said the close proximity of the U.S. official to Mr. Calzon and the Radio Marti reporter showed a "conspiracy" had been under way.

"If this had happened in Cuba they would have also thrown me in prison and said I was responsible for the disturbance," Mr. Calzon said in an interview.

Of 15 countries named by Freedom House as the world's "Most Repressive Societies," China, Cuba, Eritrea, Saudi Arabia and Sudan are commission members, while Libya chaired the body last year. It is now headed by Australia.

The 53-member commission provides guidance for the Human Rights Commissioner, the post Canadian Supreme Court Justice Louise Arbour will assume.

Members often help one another avoid censure for their country's practices. China ducked censure on a motion begun by the United States, claiming China has a far bigger population than the United States and should be allowed greater leeway.

African countries rallied to derail discussion of human rights abuses in Zimbabwe, where Robert Mugabe presides over an increasingly repressive state.

Russia lobbied heavily to have the commission reject a resolution on its actions in Chechnya, despite the discovery days earlier of the bodies of nine Chechen men who had been extrajudicially executed.

Human rights activists were dismayed to hear yesterday that Bertrand Ramcharan, acting Human Rights Commissioner, had assured Sudan he would delay official release of a UN report that concludes Sudanese government troops and Arab militias have launched a "reign of terror" against black Africans in the western Darfur region.

The news agency Reuters obtained the document this week and published its findings, but instead of being outraged by the revelations, some commission members backed Pakistan's demand that Mr. Ramcharan find out who leaked it.

"This is a joke," said Joanna Weschler, UN advocacy director of New York-based of Human Rights Watch. "The annual meeting is about to close and they have still not presented the information they have."

As in other years, only one country, Israel, has found itself the exception to the dilution, postponement or cancellation of censuring measures.

Arab and Islamist countries on the commission annually lead criticism under the title "Occupied Arab territories."

They had some competition this year as Hillel Neuer, executive director of the Geneva-based monitoring group UN Watch, pointed out the Arab territory of Lebanon was also occupied -- by Syria.

While governments rarely answer presentations by non-governmental organizations, both Syria and Lebanon demanded a right of reply. The Syrian ambassador invited Mr. Neuer to his country "to see that all live in peaceful coexistence."

Canada, which stepped down as a member this year, slammed the annual "singling out" of Israel, but also put on the international record its condemnation of Israel's recent assassination of Sheikh Ahmed Yassin, founder and leader of the terrorist group Hamas.

Mr. Neuer said Yassin was a "combatant" and Canada's terminology was "inconsistent with the right under international law to self-defence."