Police opened fire on rampaging protesters in western Nepal on Wednesday, killing at least one a day ahead of a landmark election to chart the country's political future, a police official said.

The protesters, enraged by the slaying of a candidate a day earlier, began smashing stores and vandalizing buses in the mountainous Surkhet district, prompting police to fire at them with live ammunition, said the area's police chief, Ram Kumar Khanal.

The protesters were defying a curfew imposed in the area following the killing Tuesday of the candidate, Khanal said. One of the protesters was killed Wednesday, he said.

Voting in the area has been suspended, although the rest of Nepal will hold the election as planned on Thursday. The polls are meant to cement a peace deal with former communist rebels and elect a so-called Constituent Assembly to rewrite the country's constitution.

The campaign has been repeatedly marred by violence, with the United Nations blaming the majority of incidents on the former rebels, known as the Maoists, who fought a decade-long rebellion that left some 13,000 people dead.

The slain candidate, Rishi Prasad Sharma, was a candidate of the Communist Party of Nepal (United Marxist Leninist), a political party that rivals the Maoists. Police have not yet said who they suspect in the killing.

Authorities plan to select a new polling date for the constituency where Sharma was killed about 310 miles west of Katmandu.

Violence and protests in the past year have already forced two delays in the elections, the first since King Gyanendra was forced to end his royal dictatorship by widespread unrest nearly two years ago and the Maoists declared a truce.

On Tuesday, six former rebels were killed in clashes with police in the southwestern town of Satbaria after the ex-rebels tried to attack a former minister, police said.

Police official Deepak Kumar Thapa said the situation was now under control. Initial reports had said only one person was killed in the clash.

On Monday, the last day of campaigning, bombings in two key cities wounded at least 13 people. In one attack, a motorcyclist threw a bomb near the site of an election rally in Katmandu.