Pakistan failed to properly protect former prime minister Benazir Bhutto or investigate her assassination and “severely hampered” a United Nations inquiry, U.N. investigators said on Thursday.

Bhutto was killed in a gun and suicide bomb attack after an election rally in the city of Rawalpindi on Dec. 27, 2007, weeks after she returned to Pakistan from eight years in self-imposed exile.

“While she died when a 15-and-a-half-year-old suicide bomber detonated his explosives near her vehicle, no one believes that this boy acted alone,” the 65-page report by a U.N. commission of inquiry said.

“The commission was mystified by the efforts of certain high-ranking Pakistani government authorities to obstruct access to military and intelligence sources,” it said, while noting that many officials offered full cooperation.

The three U.N. investigators, who conducted a nine-month inquiry headed by Chile’s U.N. Ambassador Heraldo Munoz, believe the failure to effectively examine Bhutto’s death was “deliberate,” the report said.

It said their inquiry had been “severely hampered” though they were still able to establish the facts and circumstances of the assassination.

“Ms Bhutto’s assassination could have been prevented if adequate security measures had been taken,” it concluded.

Bhutto was mistrusted by parts of Pakistan’s military and security establishment and speculation has lingered she was the victim of a plot by allies of General Pervez Musharraf, the president at the time, who did not want her to come to power.

The report did not say who it believed was guilty of the crime, but suggested any credible investigation should also look at those who conceived, planned and financed the operation — and should not exclude the possible involvement of Pakistan’s powerful military and security establishment.

The commission urged Pakistan to properly investigate the assassination. The government had no immediate reaction.

The report was presented on Thursday to U.N. Secretary-General Ban Ki-moon. Its release was delayed for just over two weeks because of a request by President Asif Ali Zardari, Bhutto’s widower, to allow the commission to hear evidence from three unidentified heads of state.

NO AUTOPSY, NO FORENSIC EVIDENCE

Bhutto had returned to Pakistan, a key ally to the United States in its war against al Qaeda and the Taliban, to contest an election under a power-sharing deal with Musharraf that Washington had helped to broker.

A staunch opponent of Islamist militants, Bhutto survived a bomb attack on a rally hours after arriving home in the city of Karachi in October 2007. Some 149 people were killed.

After that bombing, Bhutto had spoken of a warning from a “friendly country” she did not identify. The U.N. report said Pakistan’s ISI intelligence service told investigators it had received information from Saudi Arabia and United Arab Emirates about threats against Bhutto.

The toughly worded U.N. report said Musharraf was aware of and tracking the many threats against Bhutto.

But his government “did little more than pass on those threats to her and to provincial authorities and were not proactive in neutralizing them or ensuring that the security provided was commensurate to the threats,” it said.

It said the government treated Bhutto in a “discriminatory manner in comparison with other ex-prime ministers,” who received much more effective protection.

The report described many failures in security on the day of the assassination and the ensuing investigation.

Police deployed on rooftops on the day of the attack were supposed to have binoculars and automatic rifles, the commission said. But not a single one had binoculars or knew that he should have been carrying them.

The Rawalpindi district police hosed down the scene and did not collect or preserve evidence, preventing a proper forensic examination. The failure to conduct an autopsy has also made it impossible to determine a precise cause of death.

The actions by police were deliberate, the report said.

“These officials, in part fearing involvement by the intelligence agencies, were unsure of how vigorously they ought to pursue actions that they knew, as professionals, they should have taken,” it said.

The former government that was led by allies of Musharraf blamed the late Pakistani Taliban leader and al Qaeda ally Baitullah Mehsud for Bhutto’s murder.

Mehsud was killed in a U.S. drone strike last August. Despite the accusations against Mehsud, conspiracy theories abound in Pakistan over who was behind the assassination.

The U.N. chief set up the panel in July 2009 at the request of Pakistan’s coalition government, led by Bhutto’s Pakistan People’s Party. Its original six-month mandate was extended due to the enormity of the task.

Any criminal investigation will be up to Pakistani authorities but Munoz has said the commission’s findings could complement government efforts.

(Additional reporting by Patrick Worsnip; Editing by John O’Callaghan and Eric Walsh)