Six top Jamaat-ul-Mujahideen Bangladesh (JMB) activists, including four wanted in the 2014 Khagragarh blast case, were arrested from West Bengal and Assam.
Of the six, three were Bangladeshi nationals, Joint Commissioner of Police (Crime) Vishal Garg said here.
"These people were not in West Bengal after Khagragarh blast. They had left the state and moved to South India and North Eastern states. They were planning subversive activities in some South Indian states. We are trying to find out the details," Garg said.
The JMB activists arrested by the Kolkata Police Special Task Force included Anwar Hussain Farooq, the head of the outfit's West Bengal unit, and Yusuf Sheikh, the second in command in the state.
Sheikh, also the JMB chief motivator in the state, carried a Rs 10 lakh reward on his head announced by NIA.
The four others who were wanted in connection with Khagragarh blast of October 2, 2014, were Shahidul Islam, Mohammad Rubel, Abul Kalam and Jadidul Islam.
Kalam and Rubel were carrying on their heads a reward of Rs 3 lakh and 1 lakh respectively.
Yusuf and Shahidul were arrested from Natun Bazar under Basirhat area of North 24 Parganas district yesterday while Farooq and Rubel were picked up from Bagda Road in Bangao in the same district, Garg said.
Kalam was held from Coochbehar station in north Bengal yesterday while Jahidul was arrested from Cachhar district of Assam on Saturday.
Forged ID papers, 2 kg white powdery substance, one laptop, mobile phones, detonator, wire cutters, batteries Bangladeshi and Indian currency, letters written in Bengali, travel guide, books on chemicals and memory cards for camera were seized from them.