Balloting took place in West Tripura constituency with no untoward incidents reported so far, officials said.
"Long queues were seen in most of the 1,605 polling stations. An excellent weather helped the voters to come to the polling booths early," Tripura Chief Electoral Officer Ashutosh Jindal told IANS. He added that so far 25 percent votes were cast in the parliamentary constituency.
The balloting started at 7 a.m. and it will continue till 5 p.m.
"In some polling booths, due to technical snags of EVMs (Electronic Voting Machine), the voting was delayed for sometime, but the engineers rectified them and the balloting started as usual," Jindal said.
Election in the tribal reserved Tripura East constituency will be held April 12.
According to Jindal, 1.2 million voters are eligible to vote Monday to pick a Lok Sabha member from 13 candidates, including a woman. Almost all the candidates are first-time contenders.
In 2009, the CPI-M's Khagen Das won the seat defeating Congress's Sudip Roy Barman, state's opposition leader.
This time the main battle in the constituency will be between CPI-M's trade union leader Sankar Prasad Datta and Congress' Arunoday Saha, a former vice chancellor of Tripura University, a central varsity.
BJP state president Sudhindra Chandra Dasgupta, Trinamool Congress's state chief Ratan Chakraborty, a former Congress minister, Tripura Pragatishil Gramin Congress (TPGC) president Subal Bhowmik and Aam Aadmi Party's Salil Saha, a physician, are the other aspirants.
Both Chakraborty and Bhowmik, former Congress legislators, left the party last year and formed Tripura unit of the Trinamool and TPGC respectively.
The Left has won from West Tripura 11 times since the first Lok Sabha election of 1952 and the Congress four times. The Congress For Democracy, a breakaway faction of the Congress, secured the seat in 1977.
The ruling CPI-M this time dropped both its sitting MPs - Das and Bajuban Reang (East Tripura), who has won the seat a record seven times since 1980.
The CPI-M is focusing on the development work it has done in Tripura, while attacking the Congress led UPA (United Progressive Alliance) government for poor governance, price rise and corruption in the country.
The opposition is harping on Left's miss-governance, unemployment and rising crimes against women in Tripura.