The 54-year old Bhutto, leader of Pakistan People's Party, returned to Pakistan from an eight-year exile on Oct. 18 for the upcoming presidential elections early next year.

Shortly after the attack, Pakistani President Pervez Musharraf appealed to the nation to remain peaceful "so that the evil designs of terrorists can be defeated."

Musharraf also held an emergency meeting at the presidency to deal with the death of Bhutto, who was shot minutes after she addressed a rally of supporters in the city of Rawalpindi. The attacker blew himself up immediately after the shots.

India, whose ties with Pakistan has been unsteady in the past, condemned the murder of Bhutto, calling it a tragedy and a terrible blow to the neighbor's democratic process.

"The manner of her going is a reminder of the common dangers that our region faces from cowardly acts of terrorism and of the need to eradicate this dangerous threat," Prime Minister Manmohan Singh said in a statement.

Bhutto's death "left a deep imprint on her time and age," Singh said, adding that her desire to improve relations with India was "exemplary."

The UN Security Council is set to meet in an emergency session later on Thursday to discuss the situation in Pakistan following the killing of Bhutto, UN spokeswoman Marie Okabe said.

Okabe said the 15-member council would meet at noon (1700 GMT) to assess the situation in the country.

The European Union (EU) called the assassination "an attack against democracy and against Pakistan."

President Jose Manuel Barroso of the European Commission, the EU's executive arm, said in a statement that the bloc condemns this callous terrorist attack in the strongest terms.

"This is an attack against democracy and against Pakistan," he said. "We hope that Pakistan will remain firmly on track for a return to democratic civilian rule," he added.

The United States lashed out at the suicide attack, urging the killers to be brought to justice.

"The United States strongly condemns this cowardly act by murderous extremists who are trying to undermine Pakistan's democracy. Those who committed this crime must be brought to justice," Bush said in a statement to reporters at his Texas ranch.

A Russian foreign ministry spokesman condemned the attack, saying "we denounce the act and express our condolences to Bhutto's relatives and friends."

Mikhail Kamynin urged Pakistani authorities to do everything possible in this crucial period in order to ensure stability in the country.

David Miliband, British foreign secretary, voiced shock at the killing and called for restraint.

"In targeting Benazir Bhutto, extremist groups have in their sights all those committed to democratic processes in Pakistan. They cannot and must not succeed," he said in a statement.

France condemned the attack in sharp words, calling it "an odious act."

A statement said Foreign Minister Bernard Kouchner "expresses his deep emotion following the attack which has cost the life of Benazir Bhutto, whom he knew personally."

"He reaffirms our country's attachment to Pakistan's stability and its democracy, which should be at the center of attention for the whole international community," it said.

China also strongly condemned the Bhutto's assassination on Thursday and extended condolences to the families of Bhutto and other victims.

Several other countries including Italy, the United Arab Emirates and Afghanistan also condemned the attack.