The governor of Pakistan's central Punjab province, a senior member of the ruling party, was shot dead by one of his bodyguards in Islamabad today, plunging the country into a new political crisis.
Interior Minister Rehman Malik said, citing initial reports, said Salman Taseer was killed because of his opposition to Pakistan's blasphemy law.
Rights groups say the law is often exploited by religious extremists and ordinary Pakistanis to settle personal scores. Islamist groups have been angered by what they believe are government plans to change or scrap the law.
The shooting occurred as Prime Minister Yusuf Raza Gilani tried to muster support for the government after a leading partner withdrew from the coalition over fuel price policies.
A witness said Taseer was stepping out of his car at a shopping area when he was shot.
"The governor fell down and the man who fired at him threw down his gun and raised both hands," said the witness, Ali Imran.
The shooting left bloodstains on a parking area at Kohsar shopping centre in Islamabad, which is popular with foreigners.
Taseer, a liberal and charismatic politician close to President Asif Ali Zardari, had no day-to-day role in the affairs of the central government but his killing will add to a sense of crisis.
Earlier, the main opposition Pakistan Muslim League (PML-N), led by former Prime Minister Nawaz Sharif, said it would not demand a vote of no confidence in Gilani because to do so would aggravate instability in the South Asian country, a strategic ally of the United States.
The PML-N, believes a no-confidence vote would "damage the whole country", chairman Raja Zafar-ul-Haq told Reuters.
Sharif told a news conference he would present the government with demands such as the scrapping of fuel price rises and the dismissal of ministers accused of corruption, and gave it three days to agree, from the end of a three-day mourning period.
He threatened to evict members of the ruling Pakistan People's Party (PPP) from the Punjab provincial government, which his party dominates. Sharif suggested there might be a need for new national elections, but did not say when.
Taseer's assassination in broad daylight will reinforce the impression that the government is nowhere near stabilising nuclear-armed Pakistan.
"We will conduct a thorough investigation to know whether it was an individual act or someone else was behind it," said Malik.
The blasphemy law came under the spotlight after a court in November sentenced a Christian mother of four, Asia Bibi, to death in a case stemming from a village dispute.
The law has widespread support in Pakistan, which is more than 95 per cent Muslim, and most politicians are loath to be seen as soft on the defence of Islam.
Taseer visited Bibi in prison in a campaign for her release. He wrote on his Twitter page last Friday: "I was under huge pressure sure 2 cow down b4 rightist pressure on blasphemy. Refused. Even if I'm the last man standing."
Malik said the bodyguard, identified as Malik Mumtaz Hussain Qadri, confessed and had been arrested.
"Salman Taseer is a blasphemer and this is the punishment for a blasphemer," Qadri said in comments broadcast on Dunya television.
His hands and legs bound by nylon rope, the bearded Qadri smiled confidently as he spoke to reporters from the back of a police truck just after killing Taseer and surrendering.
Political analysts said Taseer's death would compound political tension as the opposition steps up its pressure on the government.
The second biggest opposition party also said it would not push for a no-confidence vote, suggesting the opposition might prefer to wear down a weak prime minister by blocking legislation or holding protests to force an early election.