World leaders expressed outrage at the assassination of Pakistani opposition leader Benazir Bhutto on Thursday, condemning it as a frontal attack on democracy in the Islamic republic.
US President George W Bush, whose administration has trodden a delicate line with its "war on terror" ally Pakistan, called the killing "cowardly" and telephoned Pakistan President Pervez Musharraf to offer support.
"The US strongly condemns this cowardly act by murderous extremists who are trying to undermine Pakistan's democracy," Bush said.
"We stand with the people of Pakistan in that struggle against the forces of terror and extremism."
United Nations Secretary General Ban Ki-moon described it as a "heinous crime" that "represents an assault on stability in Pakistan and its democratic processes" ahead of elections set for January 8.
The UN Security Council emerged from an emergency session on the killing with a statement condemning "this heinous act of terrorism".
Shockwaves from the assassination jolted oil prices past 97 dollars a barrel and rattled US stock markets, the Dow Jones Industrial Average falling 1.41 percent.
As at least 10 people were killed in riots which broke out in several Pakistani cities in response to the slaying, governments worldwide urged Islamabad to ensure stability ahead of the parliamentary polls.
Bhutto, a two-time former prime minister and head of Pakistan's most powerful political party, was shot in the neck by her attacker before he blew himself up at a political rally in Rawalpindi, killing at least 20 people.
It was the second suicide attack targeting Bhutto, 54, since she returned from eight years of self-imposed exile in October. The first killed 139 people.
Pakistan's neighbours, fearing an extremist spill-over if nuclear-armed Pakistan were to spiral out of control, were quick to respond.
Indian Prime Minister Manmohan Singh said Bhutto's killing was a reminder of the "common dangers" faced by India and Pakistan.
"Mrs Bhutto was no ordinary political leader but one who left a deep imprint on her time and age," he said.
Afghan President Hamid Karzai, who met Bhutto only hours before her death, called the assassination an act of "immense brutality" against one of the Muslim world's leading women.
"I am deeply sorry, deeply pained that this brave sister of us, this great daughter of the Muslim world is no longer with us," he said.
In Europe, British Prime Minister Gordon Brown said Bhutto was "assassinated by cowards afraid of democracy", while German Chancellor Angela Merkel labelled it a "cowardly terrorist attack" designed to destabilise Pakistan.
French President Nicolas Sarkozy called the assassination an "odious act," Italian Prime Minister Romano Prodi condemned the "fanaticism" that caused it and Spain spoke of a "frontal attack on Pakistani democracy."
The European Commission said the killing was "an attack against democracy and against Pakistan," while Slovenia, which assumes the rotating presidency of the European Union next week, said it could jeopardise the elections.
Russian President Vladimir Putin said he hoped "the organisers of the crime will be found and that they get the punishment they deserve".
Canadian Foreign Minister Maxime Bernier said: "The anti-democratic intent of the perpetrators could not be more obvious."
Don McKinnon, secretary-general of the 53-nation Commonwealth of which Pakistan is a suspended member, told AFP: "This is just horrible... This has thrown the whole issue of Pakistan politics into a field of uncertainty."
Reactions were equally strong throughout the Muslim world.
Turkey, a close ally of Pakistan, urged Islamabad not to stray from the path of democracy and said the killing "undoubtedly aims to draw Pakistan into chaos and instability".
In the United Arab Emirates, where Bhutto lived in exile for some years, Foreign Minister Sheikh Abdullah bin Zayed al-Nahayan said "the UAE has been tormented by this huge loss".
Iran urged authorities to track down the "terrorists" responsible, while in neighbouring Iraq President Jalal Talabani called on the world to unite against the "cancer of terrorism".
The 57-nation Organisation of the Islamic Conference, the largest pan-Islamic organisation, condemned "the outrageous and brutal murder" and the 22-member Arab League called it a "heinous terrorist crime".
Bangladesh, once known as East Pakistan, condemned the "barbaric act."
Reactions were also strong in east Asia. Chinese foreign ministry spokesman Qin Gang said his country was "shocked ... and strongly condemns the terrorist attack."
Japanese Foreign Minister Masahiko Komura said: "It is absolutely unacceptable to try to solve something by the means of violence."
Meanwhile, the Vatican said the assassination was "terrible and tragic".
In Latin America, Argentinian President Cristina Kirchner condemned what she called a "barbarous attack", while President Luiz Inacio Lula da Silva of Brazil spoke of his "great pain and indignation".