A lawyer leading the effort to prosecute Pakistan's former military dictator, Pervez Musharraf, over the murder of Benazir Bhutto has been shot dead in Islamabad as he was driving to court.

Chaudhry Zulfiqar Ali, a state prosecutor for the Federal Investigation Agency, died in a hail of bullets on Friday when his car was attacked by unidentified gunmen riding on motorbikes as he was travelling through a busy street in the Pakistani capital, police said.

He was rushed to a nearby hospital where he died of his injuries.

Ali had been acting as a state prosecutor in one of the cases against Musharraf, the former coup leader who returned to Pakistan in March for what has been a disastrous bid to contest seats in the country's general elections.

Ali argued in court that Musharraf, who is under house arrest, should not be allowed bail in a case where he is accused of conspiring to murder Bhutto, the former two-time prime minister of Pakistan who was killed in a gun and suicide attack at an election rally in 2007.

Musharraf, it is claimed, failed to use his powers as president at the time to provide sufficient security for Bhutto.

Ali was due to appear at the anti-terrorism court in the nearby city of Rawalpindi on Friday in connection with the case.

The so-far-unexplained killing of a prosecutor involved in such a high profile case is likely to excite Pakistan's national penchant for conspiracy theories.

Although Musharraf appears to have little support from the public or the political establishment, some commentators believe the military has been alarmed by his arrest and imprisonment since returning to Pakistan after four years living abroad.

In addition to the cases against him, which included another charge of killing a separatist tribal leader whilst he was president, he has also been banned from running in any of the four constituencies he hoped to contest.

This week, a court in Peshawar gave him a lifelong ban on running for public office.