"No matter how strong the militant group is, our government will take strong action against it. All those connected with the killing will be hunted out and brought to book," Sonowal told reporters after visiting the weekly Balajan Tiniali market where the massacre took place.
"Whatever evidence has been collected so far show that NDFB(Songbijit) is behind the killings", he said.
"All the security forces are coordinating the search operations and none will be spared," the chief minister said.
"It is the prime duty of the government to protect the people and their property. All will be given protection, I assure," Sonowal said.
After visiting Balajan, the chief minister went to Kokrajhar town and held a high level law and order review meeting of the Unified Command Structure's Strategic Group of civil officials, army, police and paramilitary forces.
Director General of Police Mukesh Sahay said the slain NDFB-S militant, whose body was recovered, would be identified by DNA test as his parents were unable to recognise his body as they had not seen him for the past 8-9 years.
Meanwhile, Kokrajhar Deputy Commissioner Madhu Prasad Sarma said that the killers were believed to have come from Pakriguri on the Indian side, about 10 km from Bhutan border.