National Investigation Agency (NIA) arrested an important associate of the two Khalistan Liberation Force (KLF) linked terror operatives, who carried out a grenade attack on the Thakur Dwara temple complex in Amritsar in March this year. With this, the total number of arrests in the case rose to four. Absconder Bhagwant Singh was nabbed yesterday from Akalgarh village in Amritsar.