Maoist rebels were blamed for several attacks during the first round of polls
Maoist rebels in eastern India have seized a train and taken as many as 500 passengers hostage, police say.
Up to 250 rebels boarded the train as it travelled through Jharkhand state and forced it to stop in the small town of Hegarah.
Local police told journalists that they planned to mount a rescue operation.
The incident comes on the eve of the second round of voting in India's general election. The rebels have asked people to boycott the polls.
At least 17 people were killed in attacks blamed on Maoists during the first stage of the election last week.
The hostage-takers are reportedly protesting against the death of five villagers who were allegedly shot by paramilitary troops last week.
The troops said the five were local Maoists, who were killed during a clash following an attack in which two soldiers died.
The BBC's Salman Ravi in Jharkhand says that the train, travelling between Barkakanta and Mughalsarai, was seized by a group of rebels at Barwadih station in a remote part of Palamau district early on Wednesday.
The rebels ordered the driver to take the train to nearby Hegarah station, where it was stationary when last reports came in.
"We are sending security forces to rescue the passengers," Sarvendu Tathagat, a local government official in Jharkhand, told Reuters news agency.
Earlier, the rebels also blew up a railway track near Untari railway station and a school building in Chatra district.
The rebels have called for a shut-down in Jharkhand on Wednesday.
This is not the first time rebels have seized a train in the area. In March 2006 they seized a train in Latehar, also in Jharkhand, taking more than 40 passengers hostage - but freed them 12 hours later.
Jharkhand is rich in minerals and forest resources, but its people are among the poorest in India. The rebels have a presence in 18 of the state's 22 districts.
Maoists operate in 182 districts in India, mainly in the states of Jharkhand, Bihar, Andhra Pradesh, Chhattisgarh, Madhya Pradesh, Maharashtra and West Bengal.
The rebels say they are fighting for the rights of poor peasants and landless workers.