The rebels tossed the grenade at Williamnagar police station in the district headquarter of East Garo Hills, a police official said. The incident took place at 11.30 p.m.
"There were no casualties," the police official said.
Meanwhile, police have launched a manhunt to nab the attackers. The GNLA, headed by rogue police officer-turned rebel R. Sangma, has unleashed a reign of terror in the three impoverished districts of Garo Hills in western Meghalaya.