LONDON, Dec 27 (Reuters) - World leaders voiced outrage at

the assassination on Thursday of Pakistan's opposition leader

Benazir Bhutto and expressed fears for the fate of the

nuclear-armed state.

U.S. President George W. Bush condemned the killing as a

"cowardly act" and urged Pakistanis to press ahead with a

planned national election. Russia's top Asia diplomat said the

assassination would "trigger a wave of terrorism".

British Prime Minister Gordon Brown said Bhutto had risked

everything to try and bring democracy to her country, of which

Britain used to be the colonial ruler.

"The terrorists must not be allowed to kill democracy in

Pakistan," he said.

Bhutto was killed in a gun and bomb attack as she left a

rally ahead of an election due on Jan. 8. The identity of the

attacker was not immediately clear, but Islamist militants have

been blamed for a previous assassination bid.

"The subcontinent has lost an outstanding leader who worked

for democracy and reconciliation in her country," said Prime

Minister Manmohan Singh of India, Pakistan's giant neighbour and

nuclear rival.

"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."

French President Nicolas Sarkozy called the killing odious.

"France, like the European Union, is particularly attached

to stability and democracy in Pakistan," he said in a letter to

Pakistan's President Pervez Musharraf.

FEAR

Pakistan was already a big global worry.

The U.S. ally has been struggling to contain Islamist

violence while Musharraf, whose popularity has slumped, only

lifted a state of emergency on Dec. 15 after six weeks.

Bush urged Pakistanis to honour Bhutto's memory by

continuing with the democratic process and said those behind the

attack must be brought to justice.

"The United States strongly condemns this cowardly act by

murderous extremists who are trying to undermine Pakistan's

democracy," he told reporters at his Texas ranch.

U.N. Secretary-General Ban Ki-moon said the assassination

was a "heinous crime" and an "assault on stability" in Pakistan.

The U.N. Security Council began consultations on the killing.

Jose Manuel Barroso, president of the European Union's

executive arm, the European Commission, said it was "an attack

against democracy and against Pakistan".

Police said a suicide bomber fired shots at Bhutto, 54, as

she left the rally in a park in the city of Rawalpindi before

blowing himself up. Police said 16 people died in the blast.

"It is a criminal act and is strongly condemned," Iranian

Foreign Ministry spokesman Mohammad Ali Hosseini told state

television in Pakistan's neighbour. "What Pakistan strongly

needs now is calmness and the return of stability."

A Vatican spokesman said Pope Benedict had been informed,

adding:

"It is difficult to see any glimmer of hope, peace,

reconciliation in this country."