Mining has been suspended in the entire Nongalbibra region since Monday’s attack, as officials try to reign in illegal mining and gang activity.

The five labourers were killed and others injured when the assailants armed with automatic rifles opened fire in the Darangdura coal mine area, according to a Times of India report.

South Garo Hills deputy commissioner Chinmay P. Gotmare told The Hindu that all five of the dead had hailed from lower Assam’s Goalpara district.

He said the militants were suspected members of the United Achik Liberation Army (UALA), a breakaway faction of the militant outfit Achik National Volunteer Council.

Gotmare believed the UALA had killed the men in a bid to create terror and extort money from businessmen, mine owners and others.

India has long had a problem with gang-run coal mines and the extortion of legitimate mining operations by the “coal mafia”

Reuters recently published an investigation into the country’s coal mining underbelly, revealing that the tentacles of the coal clans reached as far as state-run Coal India.

“On a series of trips to the region, Reuters found widespread plunder in India's coal country that contributes substantially to chronic shortages of a commodity fuelling over half the power generation in Asia's third-largest economy,” the report said.

Reuters said the country’s murky subculture entwined the coal mafia, police, poor villagers, politicians, unions and Coal India officials.

“Coal workers pay a cut to crime bosses to join their unions, which control access to jobs, according to law-enforcement and industry officials. Unions demand a "goon tax" from buyers, a fixed fee per tonne before loading their coal. Buyers must bribe mining companies to get decent-quality coal. The mafia pays off company officials, police, politicians and bureaucrats to mine or transport coal illegally,” the news service reported.

Coal India chairman S. Narsing Rao said he knew some of his officials were involved in stealing coal, but his company could not control what happened once trucks left the mine gate.

"Obviously it happens with the connivance of our own guys, in collusion with our own guys," he told Reuters.

Indian media has reported that the region where the latest shootings occurred was particularly prone to criminal involvement in coal mining, with a recent resurgence in criminals demanding money from mine owners under various pretexts.