Q&A: Benazir Bhutto assassination
Benazir Bhutto, twice prime minister of Pakistan, was assassinated while campaigning for elections that were scheduled for 8 January.
Ms Bhutto was a deeply controversial politician
How did it happen?
Ms Bhutto was leaving a rally of her Pakistan People's Party (PPP) supporters in a park in the garrison town of Rawalpindi when an attacker opened fire. Then a bomb was set off - either by the same attacker or a second one - which left some 20 other people dead.
The government says, however, that Ms Bhutto died as a result of banging her head on part of her car's sun roof. Her PPP party rejects this view as "dangerous nonsense", and insists she died of bullet wounds.
Rawalpindi houses the headquarters of Pakistan's military, but that has not stopped militants striking there at will. In November a suicide attack in the grounds of the much feared intelligence services left many dead.
What will be the impact in Pakistan?
Ms Bhutto was the dominant figure among Pakistan's various secular and religious political parties. She had twice served as prime minister and was hoping that the PPP would emerge as the dominant force from next month's elections, the first to be held since President Musharraf resigned as head of the army and became a civilian leader.
Ms Bhutto, Karachi, October 2007
Ms Bhutto after surviving October's blasts in Karachi
PPP activists have staged angry protests at her assassination, and many people have been killed in unrest around the country. Mr Musharraf has appealed for calm, but ordered his security forces to take tough action against rioters.
Her death has created a political vacuum.
The Bhutto name is legendary in Pakistan. Her father Zulfiqar Ali Bhutto served as prime minister but was hanged after being deposed in a coup by General Zia-ul-Haq.
Benazir Bhutto was a deeply controversial figure.
Western-educated and charismatic, she presented herself as a moderate, democratic force. As such she was widely courted in the West. The United States hoped she could restore popular legitimacy to President Musharraf's failing war against Islamist militants.
But she was widely seen as having misused her office for her own financial gain and faced a number of court cases, both inside Pakistan and outside the country. Islamist militants hated her for her pro-American views.
Earlier this year, Ms Bhutto and Mr Musharraf had been working on a power-sharing agreement. The talks failed, leaving Ms Bhutto as the biggest political threat to President Musharraf, rather than an ally.
Who could have targeted her in this way?
The government has squarely blamed a tribal leader in the lawless South Waziristan province on the Afghan border, Baitullah Mehsud, whom it describes as an al-Qaeda leader. But a spokesman for him denied any involvement, calling the accusation "government propaganda".
Nevertheless, pro-Taleban and al-Qaeda militants who have taken increasing control of Pakistan's tribal areas along the Afghan border will be the people most analysts will assume carried out the attack. They have made no secret of their determination to kill Ms Bhutto since her return to the country this year after years of self-imposed exile to escape prosecution.
On the day of her return, 18 October, a double suicide attack on her motor cavalcade in Karachi left more than 130 people dead.
What are President Musharraf's options?
Mr Musharraf has already appealed for calm as disturbances broke out in various parts of the country. One urgent decision is whether the 8 January national and provincial assembly elections should go ahead. It was only in mid-December that he ended six weeks of emergency rule during which time he sidelined leading judges who were set to rule on whether he was entitled to stay on as president.
His popularity has taken a hammering during 2007, partly because of his failure to defeat Islamist militants. Now he is no longer head of the army, it remains to be seen how the new army head, General Ashfaq Pervez Kayani, will try to deploy the army against the militants.
What is at stake for the region and the rest of the world?
The future of Pakistan is one of the keys to global security. Pro-Taleban militants and their al-Qaeda allies have become a state within a state in recent years. Militants fighting Western forces in Afghanistan and the government there of Hamid Karzai have been able to operate from within Pakistan.
Many of the major terror attacks on the West, from the 11 September, 2001, attacks in the United States, have involved people getting training and support from inside Pakistan.
Pakistan's nuclear rival to the east, India, will be watching developments with concern.