The crackdown on ULFA entered the fifth day on Sunday with the Army claiming "a fair amount of success" in the operations carried out in Assam and Arunachal Pradesh.
"The Army is continuing with its operations and has achieved a fair amount of success," an Army spokesman said refusing to divulge details.
He said several of ULFA's hideouts in Charaipung, Pengeri and in forests of Arunachal Pradesh have been busted.
While most of the camps in the forest areas were found to be abandoned, some arrests have been made from Charaipung while several linkmen of the banned group have been also apprehended, he said.
One Ali, 40, was arrested from Paglam in Dibang valley of Arunachal Pradesh where the Army believes the rebels are hiding after killing nearly 70 migrant workers in Assam. The Army on Wednesday had launched "Operation Clear" to flush out ULFA rebels.
Several copies of Swadhinata, the group's mouthpiece, and huge quantities of medicines were recovered from Ali.
"The arrest is vital as it will provide clues leading to apprehension of the ultras who are responsible for the killings."
He said the Army has identified a group of the ULFA's strike force, 28 Battalion, who were involved in the killing.
"The operations are intensive and progressing well but you cannot expect instant results."
He also confirmed media reports that hundreds of soldiers have been airlifted by choppers to reach inaccessible and remote terrains, particularly in Arunachal Pradesh's jungles.