ISLAMABAD - Two police officers were indicted Saturday in the 2007 assassination of former Prime Minister Benazir Bhutto and will face trial along with five members of the Pakistani Taliban, a state prosecutor said.

The policemen were charged with failing to provide Bhutto with proper security and with destroying evidence, said the prosecutor, Zulfikar Ali. Their indictment triggers a new trial for the Taliban members so that all seven defendants can be tried together, he said.

Bhutto and 23 other people were killed Dec. 27, 2007, in a gun and suicide bomb attack as she was leaving a rally in the garrison town of Rawalpindi. She was campaigning there to return her Pakistan People's Party to power in parliamentary elections just weeks after returning to the country from years in self-imposed exile.

A U.N. commission said the assassination could have been prevented and blamed all levels of government for failing to provide adequate security. It also accused intelligence agencies and other officials of severely hampering the investigation into those behind her murder.

The two police officers are accused of ordering the crime scene to be hosed down within minutes in what investigators believe was a deliberate attempt to destroy evidence, the prosecutor said.

A judge read out the charges against all seven defendants during a closed-door hearing at a prison in Rawalpindi, he said.

The U.N. commission's report said the Rawalpindi police's decision to hose down the crime scene and its failure to collect and preserve evidence "inflicted irreparable damage to the investigation."

The government of then military ruler Pervez Musharraf blamed Bhutto's death on Baitullah Mehsud, a Pakistani militant commander with reported links to al-Qaida who has since been killed.

But Bhutto's party has repeatedly hinted that Musharraf or his allies were involved.

Bhutto's Pakistan People's Party won the most seats in elections in February 2008 weeks after her killing. Asif Ali Zardari, Bhutto's husband, won the presidency months later after forcing Musharraf to quit the post.

The U.N. commission's report said Musharraf's government, though fully aware and tracking threats against Bhutto, did little more than pass them on to her and to provincial authorities and did not take action to neutralize them or ensure "that the security provided was commensurate with the threats."

The commission urged Pakistani authorities to carry out a "serious, credible" criminal investigation.

Pakistan later set up an investigation team of various law enforcement agencies that told the court there was evidence of Musharraf's involvement.

The court summoned Musharraf -- who has lived in Dubai and London since leaving office -- though he never appeared, resulting in him being declared a fugitive.

The Pakistani Taliban have declared a war on the state and often target Pakistani troops, government officials and minorities.

A suicide bomber heading toward a Shiite mosque was killed Saturday when his bomb detonated prematurely in southwestern Pakistan, said Hamid Shakeel, deputy inspector general in Quetta, the capital of Baluchistan province, where the blast took place.

Also Saturday, militants attacked a Pakistani army convoy in the South Waziristan tribal region along Afghan border, killing three soldiers and wounding five more, said two intelligence officials, who spoke on condition of anonymity because they were not authorized to talk to media.