ISLAMABAD, Pakistan - In a Friday morning attack that shocked this usually sedate capital, gunmen shot to death the government's top prosecutor in a case accusing former military ruler Pervez Musharraf of involvement in the 2007 assassination of former Prime Minister Benazir Bhutto, police said.

The gunmen opened fire on Chaudhry Zulfikar's car as he was leaving his home en route to an antiterrorism court in nearby Rawalpindi for trial proceedings in the Bhutto case. The shooters used either a taxi or motorbike, police said in conflicting reports.

A woman was killed when she was hit by Zulfikar's car after it came under fire, police said.

The assailants escaped, and authorities said the motive for the attack was not known.

"The police are not aware of any threats being received by the state prosecutor," said Irshad Abro, a senior police official.

Zulfikar's slaying was a rare episode of violence in the capital, which has so far seen none of the bombings or other attacks against secular politicians waged by the Taliban. The group has warned people not to vote in the May 11 national election - which will bring the first transfer of power between elected governments in Pakistan's 65-year history - saying it is against Islamic law.

In January 2011, Salman Taseer, the governor of Punjab province, was assassinated by his bodyguard at an upscale market. In May 2011, an Islamabad-based investigative reporter, Saleem Shahzad, mysteriously disappeared; his body was found about 100 miles away in a still-unsolved killing that U.S. officials linked to the Pakistani intelligence service.

Musharraf, who ruled Pakistan for nine years before going into self-exile in 2008, returned in March in an ultimately futile bid to run for prime minister. He has been under house arrest for more than two weeks, facing allegations in various cases linked to his tenure.

In the one unfolding in Rawalpindi, prosecutors allege that Musharraf was culpable for Bhutto's murder for not providing her with enough security. He has denied the allegations.

At the time, Musharraf's government blamed the Taliban for the fatal attack on Bhutto.