Abdul Karim Tunda, who was arrested on Friday by Delhi Police from the India-Nepal border, was in direct contact with Hamid Gul, a retired lieutenant general of the Pakistan Army and former spymaster who was head of the Inter-Services Intelligence (ISI) agency.
"Tunda was directly in touch with former ISI chief Hamid Gul," said a police officer.
Tunda first met with Gul in 1995 and was in regular touch with him till the day he was arrested. Gul was director general of the ISI during 1987-89.
Police will produce Tunda before a local court on Tuesday seeking his custody for further questioning.