Benazir Bhutto was killed in a gun and bomb attack after a rally in the city of Rawalpindi on Thursday, her party said.
Bhutto, 54, died in hospital in Rawalpindi. Ary-One Television said she had been shot in the head. "She has been martyred," said party official Rehman Malik.
Supporters gathered at Bhutto's former home in Dubai, where the Pakistani opposition leader spent eight years in self-imposed exile.
"We are finished," said Bair Bashir Chaudhury, a Dubai-based spokesperson for Bhutto's party. "It's almost like the party is dead."
An official of the Pakistan Business Council (PBC) in the UAE said he was shocked and saddened by the assassination.
“It’s a very shocking and sad news. I don’t think there are enough words to describe what I, and perhaps most of the Pakistani people, feel at the moment. We just pray that God will save our country from further violence,” said Dr. A. Hadi Shahid, Vice President of PBC.
Shahid, who personally met Bhutto during a business leaders’ forum in Abu Dhabi last year, said he remembers the former prime minister as a dynamic leader who understands the socio-political and economic situation of Pakistan.
“As a well-educated individual, Bhutto had a good grasp of the issues affecting our country and she tried to address those concerns within the confines of democracy. She ruled during the most challenging period in Pakistan’s history because it was after a long martial regime. We were looking forward to a better era. We were hoping she could return the democracy,” Shahid added.
He hopes that the recent development in Pakistan’s political scenario will not take its toll on their country’s economy.
“As a businessman, I believe that Pakistan’s economy is on a solid foundation. After a number of years, the country has managed to draw a clear line between politics and economy. Whatever is happening on the political side should not dampen the country’s economic development,” Shahid said.
Dubai residents expressed shock at today's news. “Bhutto was a very, very well known politician. It was her birthday last year and we just happened to attend the party and I met her. [Her death] is definitely a loss,” one Pakistani national told Emirates Business.
Police said a suicide bomber fired shots at Bhutto as she was leaving the rally venue in a park before blowing himself up.
"The man first fired at Bhutto's vehicle. She ducked and then he blew himself up," said police officer Mohammad Shahid.
Police said 16 people had been killed in the blast.
"It is the act of those who want to disintegrate Pakistan because she was symbol of unity. They have finished the Bhutto family. They are enemies of Pakistan," senior Bhutto party official Farzana Raja told Reuters.
A Reuters witness at the scene of the attack said he had heard two shots moments before the blast. Another Reuters witness saw bodies and a mutilated human head strewn on a road outside the park where she held her rally.
A spokesman for President Pervez Musharraf said he had to confirm the news before commenting.
Earlier, party officials had said Bhutto was safe.
A suicide bomber killed nearly 150 people in an attack on Bhutto on October 19 as she paraded through the southern city of Karachi on her return from eight years in self-imposed exile.
Islamist militants were blamed for that attack but Bhutto had said she was prepared to face the danger to help the country.
People cried and hugged each other outside the hospital where she died and residents of Karachi, Bhutto's home town, said they had heard gun shots after news of Bhutto's death spread, apparently from her enraged supporters.
Bhutto's father, Zulfikar Ali Bhutto, was Pakistan's first popularly elected prime mister. He was executed in 1979 after being deposed in a military coup.
Bhutto became the first female prime minister in the Muslim world when she was elected in 1988 at the age of 35. She was deposed in 1990, re-elected in 1993, and ousted again in 1996 amid charges of corruption and mismanagement.
She said the charges were politically motivated but in 1999 chose to stay in exile rather than face them.
Bhutto's family is no stranger to violence. Both of her brothers died in mysterious circumstances and she had said al Qaeda assassins tried to kill her several times in the 1990s.
Intelligence reports have said al Qaeda, the Taliban and Pakistani jihadi groups have sent suicide bombers after her.
A top Russian diplomat was quoted by Reuters as saying that Bhutto's killing could trigger a wave of terror in the country.
"An act of terror is a bad sign," Deputy Foreign Minister Alexander Losyukov, Russia's most senior Asia diplomat, told Itar-Tass news agency. "We hereby offer our condolences. This will for certain trigger a wave of terrorism."