necessitated following stepped up attempts by militants of the Isak-Muivah faction of the National Socialist Council of Nagaland (NSCN) to disturb the election process," Nagaland police chief Heso Mao told IANS by telephone from state capital Kohima.
"Troops have been issued instructions to strictly deal with anyone found violating the curfew."
Nagaland is among four other Indian states that go to the polls Wednesday.
The police chief said at least six ruling Congress party members were kidnapped at gunpoint by NSCN (Isak-Muivah) militants Monday in the western Peren district, while a lady Congress leader was assaulted in public by rebels belonging to the same outfit.
On Saturday and Sunday, at least 15 Congress party supporters were abducted by NSCN militants from two different places.
"We are yet to get any news of the abducted Congress members. The NSCN (Isak-Muivah) militants were reportedly threatening and intimidating voters not to support Congress candidates in the polls," Mao said.
The curfew would be relaxed from 5 A.M on Tuesday and re-imposed after sunset.
"The curfew is an attempt at reassuring voters that militants cannot move freely during the night when most intimidations and threatening takes place," the police chief said.
The NSCN, fighting for an independent tribal homeland, is operating a ceasefire with the federal government since 1997.
Guerrilla leaders of the NSCN, Isak Chishi Swu and Thuingaleng Muivah, was in New Delhi last month for peace talks to bring an end to more than five decades of violent insurgency in this mountainous region.
The official said NSCN (Isak-Muivah) cadres have also forcibly commandeered a number of vehicles belonging to Congress members and supporters in the state.
The NSCN leaders, Isak and Swu, had earlier said they would not interfere in the elections - either directly or indirectly.
The Congress accused the NSCN (Isak-Muivah) of openly supporting candidates put up by the Bharatiya Janata Party (BJP) and the National People's Front (NPF), a regional political party.
"The BJP and the NPF are being supported openly by the NSCN and they want the win the polls with the help of guns. But people in Nagaland cannot be taken for a ride," Nagaland chief minister and senior Congress leader S.C. Jamir told IANS by telephone from Mokokchung.
"It is a democracy and people would not be cowed down by such threats."
Elections in Nagaland have always been overshadowed by militancy with underground groups siding with political parties.
More than 25,000 people have lost their lives to insurgency in Nagaland since India's independence in 1947.