Five people were killed, including four in the firing by CISF personnel, during the fourth phase of polling on Saturday for 44 assembly seats of West Bengal, triggering a political firestorm.

An estimated 52.89 per cent of 1.15 crore voters exercised their franchise till 1 p.m.

Four people were killed as central forces opened fire allegedly after coming under attack from locals, who "attempted to snatch their rifles", in West Bengal's Cooch Behar district, police said.

The Election Commission ordered stopping the voting exercise at polling station number 126 in Sitalkuchi where the incident happened when polling was underway.

"According to 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. Further details are awaited," a police official said.

The EC has sought a detailed report on the incident.

According to official sources, the preliminary report submitted by EC's special police observer Vivek Dubey said a huge mob of around 350-400 people had gheraoed the central forces, following which they fired in "self-defence".

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

In another incident, an 18-year-old voter, Ananda Barman, was gunned down outside booth number 85 in Pathantuli, also in Sitalkuchi, after clashes broke out between activists of the ruling TMC and the BJP.

Condoling the deaths in Cooch Behar, Prime Minister Narendra Modi Saturday requested the Election Commission to take stern action against those responsible for the incident and blamed the ruling TMC for perpetrating violence during the polls.

He also accused Chief Minister Mamata Banerjee of instigating people against the central forces.

"What happened in Cooch Behar is unfortunate and sad. I extend my condolences to the bereaved families and urge the Election Commission to take stern action against those responsible.

"Mamata Didi and her TMC goons have become jittery because of ground swell of support for BJP," Modi told an election rally in North Bengal's Siliguri.

Chief Minister Mamata Banerjee demanded the resignation of Home Minister Amit Shah and a reply from him on firing by the central forces which led to the death of people "standing in the queue to vote".

Asserting that she had apprehended such an incident all along, Banerjee said, "After killing so many people, they (Election Commission) are saying the firing was in self- defence. They should feel ashamed."

"This is a lie....the CRPF opened fire on people standing in the line for voting, killing 4 in Sitalkuchi. I had been apprehending the forces would act in such a manner for long. As the BJP knows it has lost the people's mandate, they are conspiring to kill people," she said at a rally in North 24 Parganas.

The chief minister said she will visit the scene of the incident.

In the 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, the officials said.

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

In Bangor in South 24 Parganas, clashes were reported between ISF and TMC workers after the former alleged the ruling party was not allowing their polling agents to enter the booth.

In Chanditala in Hooghly, CPI(M) activists scuffled with TMC supporters outside a booth.