Police officials say the attack was aimed at disrupting Bihar's elections [File]

Six Indian police officers have been killed by a roadside bomb allegedly planted by Maoist rebels in the country's east, officials say.

The mine exploded as the officers' jeep passed under a bridge in the Sheohar district of Bihar state on Saturday. The policemen were returning to their base after inspecting security arrangements for local elections this weekend.

Police officials said the attack aimed to disrupt the month-long polling process to elect a new government for Bihar, which began its first phase on Thursday.

"The land mine attack was aimed to create terror among the voters," Neelmani, Bihar's director general of police, who asked reporters to call him by only one name, said.

The police have launched an operation to catch the suspected attackers.

The Maoist rebels, also known as Naxals, have called for a boycott of the polls and put up posters in the district urging people not to vote.

The group has been fighting the government for more than four decades, demanding more land and jobs for the poor.

Manmohan Singh, the country's prime minister, has called the rebel group, which regularly ambushes police, the country's biggest internal security threat.