A U.N. report on the killing of former Lebanese Prime Minister Rafik Hariri (search) says Lebanese authorities bungled, if not outright manipulated, their probe of his death and demands a new international investigation.

The report does not directly blame Syria for the assassination of Hariri, an opponent of the Syrian presence in Lebanon, but says Damascus was behind the political tension and weak security that led to his death — and that of 17 other people — in a huge explosion on Feb. 14.

"Clearly, Mr. Hariri's assassination took place on the backdrop of his power struggle with Syria, regardless of who carried out the assassination and with what aim," the report released Thursday says. The U.N.-backed investigation was led by deputy Irish police commissioner Peter Fitzgerald.

Opposition leaders and foreign officials fear Hariri was killed for opposing pro-Syrian President Emile Lahoud (search), who was allowed to stay in office for another term after parliament rewrote the constitution with Syria's approval.

Hariri had also supported Security Council resolution 1559 (search), which demanded Syria withdraw its forces from Lebanon. It also said the council hoped Lebanon's upcoming elections would be free of foreign influence — a reference to Syria, which has held enormous political influence in Lebanon since its troops entered the country in 1976.

While Fitzgerald's report accuses Syria of creating the conditions for Hariri's death, it reserves withering criticism for Lebanese authorities who handled the case.

The report says there was a "distinct lack of commitment" by the authorities to investigate the crime, and the probe was not carried out "in accordance with acceptable international standards."

It detailed a host of flaws, including the disappearance of crucial evidence and tampering with the scene of the blast. Parts of a pickup truck were brought to the scene, placed in the crater and photographed as evidence, it said.

The report alleged investigative judges had no control over the probe and even faulted police for not turning off a water main that flooded the blast crater and washed away vital evidence.

Studying the aftermath of the bombing, Fitzgerald's team also cast serious doubts on the legitimacy of a suspect, a Palestinian named Ahmed Abu Adas (search), and a group that claimed responsibility, the little-known Support and Jihad in Syria and Lebanon.

Fitzgerald also faulted Syria for interfering in the governing of Lebanon "in a heavy-handed and inflexible manner." He said his investigators also received testimony that Syrian President Bashar Assad (search) had threatened Hariri and leading opposition figure Walid Jumblatt (search) with physical harm.

Syria's U.N. Ambassador Fayssal Mekdad rejected the report, saying it contained "too much rhetoric." He denied his country had any role in Hariri's assassination.

Fayssal called Hariri a "great ally of Syria" and instead blamed the U.N. Security Council for passing resolution 1559.

"We think that things were going on well in Lebanon until a certain development that has taken place here in this building when one, two countries pushed the council to adopt a resolution that was not called for," Mekdad said from the United Nations in New York.

In Beirut, Lahoud said he had told U.N. Secretary-General Kofi Annan to do "what is necessary" to learn who was behind Hariri's death.

In a letter accompanying the report, Annan expressed full support for the findings. He backed its recommendation for an international independent commission with the authority to interrogate witnesses, conduct searches and other tasks.

Lebanon's opposition and Hariri's family have insisted on an international investigation, saying they have no trust in the Lebanese probe.

The report reflected that sentiment, saying the Lebanese investigation "lacks the confidence of the population necessary for its results to be accepted."

The U.N. Security Council is now expected to take up the issue. It would have to approve a resolution seeking a new investigation, and would most likely ask Annan to appoint a new team.

Hariri's killing led to political turmoil in Lebanon, and subsequent mass demonstrations forced the resignation of the Lebanese government. The protests and intensified the international campaign for Syria to withdraw its troops from the country.

Syria has now pulled back its troops and intelligence agents into eastern Lebanon toward the border and has been promising to work out their complete removal with Lahoud's pro-Syrian government in Beirut.