Four persons were killed as CISF personnel allegedly opened fire after coming under attack from locals, who "attempted to snatch their rifles", in West Bengal's Cooch Behar district on Saturday, hours after an 18-year-old voter was allegedly gunned down by miscreants outside booth number 85 in Pathantuli area of the same district.

The incident involving the CISF took place in Sitalkuchi area when voting was underway, a senior police officer said.

"As per preliminary reports, four persons were killed as CISF personnel opened fire after coming under attack in a village.

"A scuffle took place and locals gheraoed them and attempted to snatch their rifles, following which the central forces opened fire," he said.

Condemning the incident, the Election Commission on Saturday ordered adjournment of polls at polling station number 126 in the Sitalkuchi Assembly constituency of Bengal amid reports of violence.

A spokesperson of the poll panel said the decision was based on an interim report filed by special observers. Detailed reports have been sought from them and the state Chief Electoral Officer by 5 pm.

Meanwhile, A first-time voter was allegedly shot dead on Saturday in Cooch Behar district of West Bengal, where 33.98 per cent voter turnout was recorded till 11 am in the fourth phase of assembly elections amid sporadic incidents of violence, officials said.

Ananda Barman was allegedly gunned down by miscreants outside booth number 85 in Pathantuli area after clashes broke out between activists of the ruling TMC and the BJP.

The culprits, who are yet to be identified, managed to flee, the officials said.

The incident led to violence in the area as bombs were hurled, prompting central forces to baton-charge to bring the situation under control, police said.

Both the TMC and BJP claimed that Barman belonged to their party, but his family members said he was an activist of the saffron party.

"We have received information about a person being shot outside a polling booth in Sitalkuchi in Cooch Behar. We have sought a report from the micro observer," an Election Commission official said.

The Trinamool Congress has moved the EC, complaining against the BJP of not allowing its agents to enter several booths at Coochbehar's Natabari, Sitalkuchi, Tufanganj, Mathabhanga and Dinhata.

The BJP has denied the allegations.

In Ganguly Bagan area in Jadavpur constituency, the booth agent of CPI(M) candidate Sujan Chakraborty was reportedly attacked by a "fake voter", who threw chilli powder at her while trying to escape, the officials said.

A central police contingent was rushed to the spot following the incident.

Meanwhile, BJP candidate Indranil Khan accused the central forces of not taking action against bogus voters in Kasba constituency in Calcutta.

Over 1.15 crore voters are eligible to exercise their franchise to decide the fate of 373 candidates, including Union minister Babul Supriyo and state ministers Partha Chatterjee and Arup Biswas.

Voting will continue till 6.30 pm.

Tight security arrangements have been made to ensure peaceful voting with 789 companies of central armed police forces (CAPF) being deployed to guard 15,940 polling stations.