REUTERS, KATHMANDU - Nepal deployed helicopters on Saturday to guard a tense campaign for next week's constituent assembly elections that could lead to the abolishment of the centuries-old monarchy.

About 135,000 police will keep watch on the April 10 vote for the assembly, a key demand of the Maoist former rebels who ended their decade-long civil war in 2006, meant to prepare a new constitution and most likely turn the Himalayan nation into a republic.

Fear of violence has overshadowed the country's first national election in nearly nine years - at least three people have so far died in election-related violence. Scores others have been injured in clashes between rival parties, many involving the Maoists.

Many armed rebel groups fighting for greater autonomy in Nepal's southern plains bordering India are opposing the vote and have vowed to disrupt the polls in the region where scores of people were killed in violence in the past year.

"Helicopters carrying armed police personnel will conduct regular air patrols watching for any sign of trouble on the ground until the polling is over," Modraj Dotel, Home (interior) Ministry spokesman, said on Saturday.

"The aerial patrolling which began on Saturday will continue until the election day after which the same helicopters will transport ballot boxes from remote polling stations to the district headquarters for counting."

Dotel said the 100,000-strong army would not be used for election duty under the deal with the Maoists who have confined thousands of their former fighters to U.N.-monitored camps and joined the fray. Nepal does not have an air force.