Gunmen killed Pakistan's lead prosecutor investigating the assassination of former prime minister Benazir Bhutto as he was driving to court Friday, throwing a case that also involves the country's former ruler Pervez Musharraf into disarray.

The killing in the capital, Islamabad, comes at a sensitive time in Pakistan, as the country prepares for nationwide elections on May 11 amid a spate of Taliban attacks on candidates. In the southern city of Karachi, gunmen on motorcycles killed an anti-Taliban election candidate and his son, and a political activist in two other attacks Friday.

The government prosecutor who was gunned down, Chaudhry Zulfikar Ali, was at the helm of a number of highly controversial cases, including the 2007 Bhutto assassination in which Musharraf is accused of involvement. He was also prosecuting militants linked to the 2008 terror attack in the Indian city of Mumbai.

Ali was on his way to a court in Rawalpindi, next to Islamabad, when gunmen fired at him, hitting him in the head, shoulder and chest, and then fled in a taxi and on a motorcycle, said police officer Arshad Ali. The prosecutor was shot at least 13 times and his car was pockmarked with bullets and the windshield shattered.

He then lost control of his car, which hit a woman passer-by and killed her, said another police officer, Mohammed Rafiq.

Ali's guard returned fire and is believed to have wounded at least one of the attackers, Rafiq said. The guard also was injured in the attack. Police have launched a search to find and apprehend the gunmen.

Though Pakistan has experienced rampant violence in recent years, it's rare for such an attack to happen in the capital, which is home to high-ranking government and military officials, diplomats and international aid workers.

Bhutto's husband, President Asif Ali Zardari, strongly condemned the prosecutor's slaying and called for a thorough investigation.

A motive for the killing was unclear, but Ali's involvement in the two particularly high-profile cases will likely be scrutinized closely.

Government prosecutors have accused Musharraf of being involved in the Bhutto assassination and not providing enough security to Pakistan's first female prime minister. Musharraf, who was in power when Bhutto was killed, has denied the allegations. At the time of the attack, he blamed the assassination on the Pakistani Taliban.

The Bhutto case has lingered for years in the Pakistani court system. A number of alleged assailants are on trial but no one has been convicted. The case burst into the headlines when Musharraf returned in March after four years in exile.

The prosecutor told reporters that he had received death threats recently in connection with the case but would not say who from or what they said.

Ali was also the government's lead prosecutor in a case related to the 2008 terrorist attack on the Indian city of Mumbai that killed 166 people. The attack was blamed on the Pakistan-based militant group Lashkar-e-Taiba.

Pakistan has put seven men on trial on charges they assisted in the Mumbai siege, but the trial has made little progress. India has criticized Pakistan for not doing more to crack down on the militants blamed for the attack. Hafiz Saeed, the head of a group believed to be a front for Lashkar-e-Taiba, remains free, and many believe he enjoys the protection of the government. Lashkar-e-Taiba was founded years ago with the help of Pakistani intelligence to put pressure on India over the disputed territory of Kashmir.

Musharraf returned to Pakistan to make a political comeback despite Taliban death threats and a raft of legal cases against him. But his fortunes have gone from bad to worse since he arrived.

Judges barred him from running in the May 11 parliamentary election not long after he arrived because of his actions while in power. A court in the northwestern city of Peshawar went further this week and banned Musharraf from running for public office for the rest of his life _ a ruling the former military strongman plans to appeal.

Musharraf is currently under house arrest on the outskirts of Islamabad in connection with several cases against him, including the Bhutto case. He also faces allegations of treason before the Supreme Court.

Ali was headed to a hearing related to Musharraf and the Bhutto case at a court in Rawalpindi when he was killed.

Musharraf seized power in a military coup in 1999 when he was serving as army chief and ruled for nearly a decade until he was forced to step down in 2008 because of growing discontent with his rule.

In Karachi, gunmen riding a motorcycle shot to death Sadiq Zaman Khattak, who was running for parliament from the Awami National Party, and his six year-old son, said police officer Mohammad Ali.

The attack occurred as Khattak was leaving a mosque after Friday prayers. Four people were wounded, said Ali, the police officer.

The Awami National Party has been repeatedly targeted by the Taliban in the run-up to the election because of its opposition to the militants. The Taliban have threatened two other secular parties as well, including the Muttahida Qaumi Movement, which controls Karachi.

In the second attack in Karachi, gunmen riding on a motorcycle killed a prominent activist from the Muttahida Qaumi Movement, Mohammad Adil, outside a different mosque, said police officer Mohsin Khan.

No one has claimed responsibility for the attacks.

The May 11 election is historic because it will mark the first time in Pakistan that a civilian government has finished its term and handed over power in democratic elections. Pakistan has experienced three coups, including the one led by Musharraf in 1999. (AP)