The National Investigation Agency (NIA) on Thursday attached the Srinagar property of Mushtaq Ahmad Zargar, founder and chief commander of Al Umar Mujahideen. Zargar was released, along with JeM chief Masood Azhar, in exchange for passengers of the hijacked Indian Airlines flight 814 in Afghanistan's Kandahar in 1999. Zargar was responsible for several terror attacks in J&K, an official said.