At least seven persons were killed and an equal number injured after heavily armed militants opened an indiscriminate fire on a group of people in India's north eastern state of Assam, police sources said Monday. Police sources said the incident happened late Sunday night when a group of people were gambling on the occasion of Diwali festival in Assam's Goalpara district. "The militants suddenly appeared and opened fire on them. Six people died while on their way to hospital. Another person succumbed to injuries on Monday morning," sources said, adding, "The rest of the seven injured persons have been hospitalised". The preliminary investigations have revealed that the heavily armed militants were part of Garo National Liberation Army (GNLA), the sources said. GNLA has been declared proscribed group by the government and is active in the Garo hills jungles of Meghalaya, adjacent to Goalpara district, the sources said, adding, the militant group has been fighting for a separate state since 2009 indulging in killings, attacks on security forces and civilians, blasts, and kidnappings. Soon after the incident, the government tightened the security in the area, they revealed. "The administration has also imposed indefinite night curfew in the area. The police and army are screening the area to trace out the attackers," sources informed.