Guwahati, Feb 7 (PTI) The National Investigation Agency (NIA) on Friday interrogated IIT-Guwahati professor Arupjyoti Saikia for the fourth time in a week in connection with the violence during the protests against the CAA here last month.

Saikia, a professor of History at the Indian Institute of Technology-Guwahati, was summoned to the NIA office in Sonapur in the outskirts of the city.

"Today he was questioned for several hours. He is being questioned as a witness to Akhil Gogoi's case," his advocate Santanu Borthakur told PTI.

Saikia was first questioned on February 1.

Krishak Mukti Sangram Samiti (KMSS) advisor Hussain Md Shahjahan was also quizzed for the third time during the day.

Pranjal Kalita, former general secretary of the Cotton University Students' Union, was grilled for about six hours by an NIA team on Thursday in connection with the violence during the protest against the contentious Citizenship (Amendment) Act in December.

He is the assistant general secretary of the Satra Mukti Sangram Samiti, the students' wing of the KMSS.

All of them are being interrogated in a case related to alleged "terror activity" by peasant leader Akhil Gogoi, who is the advisor of the KMSS.

The NIA has already arrested around half a dozen senior leaders of the KMSS and its sister organisations for their alleged role in the violence.

Gogoi was arrested on December 12 from Jorhat as a "preventive measure" in view of the deteriorating law and order situation in the state and his colleagues were taken into custody the next day.

However, the Assam Police registered an FIR on December 13 at the Teok police station. In an abrupt decision, the case was handed over to the NIA the following day.

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