Agartala, Jun 23 (IANS): Amid stray incidents of violence, by-elections to four Assembly constituencies in Tripura were underway on Thursday with 68.37 per cent turnout recorded till 3 p.m.

A police spokesman said that police constable Samir Saha was stabbed by unknown miscreants at Ujan Abhoynagar under Agartala assembly constituency. Family members of Saha, who was admitted to the hospital in a critical condition, alleged that ruling BJP goons attacked him.

There were reports of intimidation, and clashes in different places of Agartala, Town Bordowali, Surma, and Jubarajnagar Assembly constituencies in three districts -- West Tripura, North Tripura and Dhalai.

Opposition parties including Trinamool Congress, Congress and CPI-M-led Left have alleged that BJP supporters and their goons have launched a series of attacks, intimidated and prevented people from voting and indulged in booth capturing while security forces did nothing.

The BJP leaders, however, denied the allegations.

Central and state security forces were deployed to hold the vital by-elections being termed as a 'semi-final' before the elections to the 60-member Assembly early next year.

In all, the 1,89,032-strong electorate would decide the political fortune of 22 candidates including seven women.

The month-long campaign for the by-polls was also marred by violent incidents. Former BJP minister Sudip Roy Barman, who is now contesting from the Agartala constituency on a Congress ticket, was injured when "BJP activists" allegedly attacked him late on Sunday night. Barman, a five-time MLA from Agartala constituency, is under treatment even as he is supervising the electioneering.

The by-polls were necessitated after the resignation of three BJP MLAs and the death of CPI-M legislator Ramendra Chandra Debnath.

The votes will be counted on June 26.