Another forest guard was attacked in the Laokhowa Wildlife Sanctuary in Nagaon by unidentified persons.
The forest guard has been identified as Islam Ali.
According to forest officials, Islam was attacked late in the evening of Monday when he was coming back from a market to the camp.
He was beaten up by a group of five to six unidentified persons.
Islam was recovered by his colleagues later in the evening and was immediately taken to a medical facility in Dagaon.
He is said to be in a critical condition but treatment is on.
A forest official said that the incident took place in the same where two other guards were attacked recently.
The official said that the department suspects the culprits to be illegal fishermen of the nearby village.
He informed that Ali had told them about it after being recovered.
One of the attackers had mentioned the forest department barring illegal fishing inside the sanctuary while attacking him.