A mob of Indian workers has beaten the CEO of a jute factory to death in a dispute over increasing their working hours, police told the AP news agency after arresting six workers.

Four suspects were arrested on Sunday, followed by two on Monday, and are expected to be charged with murder, vandalism and other crimes.

A group of 200 workers, wielding iron rods and stones, stormed the office of 60-year-old HK Maheswari in the eastern Indian state of West Bengal, according to Sunil Chowdhury, the Hooghly district superintendent.

Maheswari had denied their earlier request to work and be paid for 40 hours a week at the North Brook Jute Mill, instead of the current norm of 25.

He had also proposed shutting down the mill for three days a week to limit mounting financial losses, according to the factory's general manager, Kiranjit Singh.

"The mill workers suddenly resorted to stone pelting while we were busy in a meeting," Kiranjit Singh told AP.

At one point during Sunday's meeting, Maheswari looked out the window at the growing crowd and was struck in the head by two stones.

He collapsed, at which point a large group of workers stormed the office, Singh said.

"The CEO was thrashed with iron rods, and he succumbed to his injuries very soon," Singh said.

Both the general manager and a security guard were treated at hospital, while Maheswari died on the way to a hospital, police said.

West Bengal is known for its combative labour unions backed by political parties, and chief minister Mamata Banerjee immediately blamed the violence on unions run by opposition parties.

The opposition has denied any role in the attack, and said an independent investigation should be held before any blame is hurled.

On Monday, Banerjee sought to reassure the business community that her government did not tolerate union violence.

Meanwhile, work at the mill has been suspended indefinitely. A funeral was planned for Tuesday for Maheswari, who is survived by his wife, two grown daughters and a son.