Three militants of the United National Liberation Front (UNLF), an outlawed separatist outfit from the northeastern state of Manipur, were arrested at the Indira Gandhi International Airport on Wednesday morning.
The three, identified as Jayant Kumar, Ghanshyam Kumar and Shyam Kumar Singh, were reportedly travelling to Kathmandu, Nepal, on forged documents.
They were arrested by Delhi Police with assistance from the Intelligence Bureau.
According to police, a pen drive was seized from the militants that stored detailed information on the Indian Army and paramilitary force deployments in the northeast.
Said Deputy Commissioner of Police (Special Cell) Alok Kumar: "The pen drive had information on the names of army and Central Reserve Police Force (CRPF) officials, apart from details of force deployment in the northeast."
He added: "It also had details of the UNLF organisational structure, names of their cadre leaders and funding details."
Security had been stepped up at 13 Indian airports Tuesday following a terror hijack threat.