The armed insurgents swooped on the group of gamblers at remote Gendamari in Aagia police station and randomly fired on them from automatic weapons at around 9 PM.
Bholanath Rabha, Amarendra Rabha, Jayanta Rabha, Puran Rabha, Kalpanath Rabha and Lulu Rabha died on the spot, official sources said.
The injured were rushed to Goalpara Civil Hospital by the local people who alleged that the police came late at the site of the firing.
Meanwhile, senior police officers have rushed to the spot from the district headquarters town of Goalpara and security has been beefed up in the district following the incident, the sources said.
Goalpara district has been witnessing violence since October 20 with protests against the upcoming Rabha Hasong Autonomous Council elections between November 13 and 25 demanding exclusion of non Rabha areas from the Council.
The sources, however, ruled out that tonight's incident was connected with the Council elections.
Proscribed GNLA, based in the jungles of Garo Hills district of Meghalaya near Goalpara district, has been fighting for a separate state since 2009.
They attack security forces and civilians, trigger blasts and kidnap people to extort money.