''A group of ten to 12 GNLA militants armed with automatic weapons at around 0030 hours (IST) fired indiscriminately at Dobu police outpost,'' Superintendent of Police J F K Marak told UNI.
Mr Marak said the firing which lasted for about 30 minutes did not damage the structure of the outpost.
According to the police, the militants were led by Meghalaya Police constable Savio R Marak, who had deserted his police rank and aligned himself with the militant outfit.
Following the attacked, Mr Marak said a security alert has been sounded in the district.
Meanwhile, police have launched a combing operation in the area to flush out the militants from the area.
The GNLA is led by Champion R Sangma, a trained 'deputy superintendent of police'-turned-rogue, who has been fighting for 'sovereign Garoland' in Western Meghalaya.
The nascent outfit militant was maintaining a close operational relationship with other Northeast-based militant outfits-- ULFA and NDFB.