By Joseph Guyler Delva

PORT-AU-PRINCE, Haiti, Oct 14 (Reuters) - Haiti's human rights situation is "catastrophic," with summary executions, mob violence, torture and arbitrary arrests, the top U.N. human rights official in the troubled Caribbean nation said on Friday.

Thierry Fagart called on Haiti's U.S.-backed interim government, appointed after the ouster of President Jean-Bertrand Aristide in February 2004, to end human rights abuses immediately.

Fagart, a French lawyer who heads the human rights section of the U.N. mission in Haiti, said defenseless people were being hacked and burned to death by mobs that sometimes acted with the connivance of Haitian police.

"This situation is catastrophic. It is so catastrophic that it needs to be corrected rapidly," Fagart told reporters during a news conference in the capital.

In December Haiti is expected to hold its first elections since Aristide's departure

Aristide, a former priest who became Haiti's first freely elected president in 1991, was serving his second term when he was forced into exile on Feb. 29, 2004, by a bloody rebellion and pressure from the United States and France.

An interim government was installed and U.N. peacekeepers were sent to the impoverished nation but hundreds of people have been killed in political and gang violence that foreign observers fear could damage chances for a fair election.

Fagart cited as evidence of the poor human rights situation a spate of killings in the Martissant area of Port-au-Prince on Aug. 20. A U.N. inquiry by under Fagart's supervision found at least 10 people were killed by Haitian police and civilians with machetes.

Other killings in Aristide's slum strongholds also have been blamed on the Haitian police, an ill-trained civilian force that crumbled in the face of armed gangs and former soldiers who took over large areas of the country last year.

U.N. officials said physical abuse of people in police custody and of inmates by prison guards are common.

Police Chief Mario Andresol said this week that a number of police officers were involved in killings, kidnappings and other criminal activities. He said 15 policemen were going to be prosecuted for such crimes.