Professor M Gias Uddin Ahsan’s nephew Alam Chowdhury, and Mahbubur Rahman Tuhin, the manager of a house in Bashundhara Residential Area were also arrested on Saturday.
DMP Deputy Commissioner Masudur Rahman said they were arrested at the House 3 at Block-E on Road-6 in the area around 5:30pm.
He said five militants who carried out the attack on Gulshan cafe on July 1 had taken shelter in the flat No. A/6, owned by Ahsan.
Several cartons loaded with sand and the dresses they left behind were seized from the flat.
Police suspect the cartons were used to keep the grenades used in the attack that left at least 20 hostages and two policemen dead.
Ahsan’s nephew Alam and manager Tuhin were tasked with renting the flat.
“But they did not follow the DMP instruction to collect tenants’ info while renting the flat,” DC Rahman said.
Ahsan is the dean of NSU’s School of Health and Life Sciences, according to the private university’s website.
DC Rahman said police’s counterterrorism unit, which is investigating the Gulshan attack, arrested the trio.
The unit’s Deputy Commissioner Saiful Islam told bdnews24.com a person rented the flat in May.
They suspect he is a member of Jama’atul Mujahideen Bangladesh (JMB).
“The man fled the flat on the day of Gulshan attack. It appears from the information we have got initially that some of the Gulshan cafe attackers had come to this house.”
He said police would produce the trio before a court on Sunday and seek 10 days to grill them.
Security forces killed six persons in the raid to rescue the Gulshan cafe siege hostages.
One of them, Nibras Islam, was a student of North South University. His family said he had been missing for months.
A freed hostage, Hasanat Reza Karim, was a teacher of the university. He was sacked reportedly for his links to banned Islamist organisation Hizb-ut Tahrir.
His family has alleged that police did not release him with the other hostages and he has been unaccounted-for since then.
After the Gulshan attack, police released a list of 10 youths missing for months, suspecting their links to terrorism.
Two of them - Mohammad Basharuzzaman from Rajshahi and Junnun Shikder from Jigatola in Dhaka – were also students of NSU.
A check post guarding Bangladesh’s largest prayer congregation at Kishoreganj’s Sholakia came under attack on Eid day.
Two police constables died after being hacked and bombed by attackers. One of the attackers was gunned down.
He has been identified as NSU student Abir Rahman. His family said he had been missing for four months.
The university came under scrutiny after the killing of blogger and Ganajagaran Mancha activist Ahmed Rajib Haider in 2013. The young men arrested for hacking him down were all students of the Electronics and Electrical Engineering (EEE) at the university.
They are Sadman Yasir Mamun, Faisal Bin Nayeem Dwip, Ehsan Reza Rumman, Maksudul Hasan Anik, Nayeem Irad and Nafiz Imtiaz.
Quazi Mohammad Rezwanul Ahsan Nafis, who tried to blow up the New York Federal Reserve Bank in 2012, was also a student of NSU before he migrated to the United States.
A four-member team from the University Grants Commission (UGC) visited the private university campus at Bashundhara last Thursday.
The visit was a part of an investigation into the university’s link with terrorism, officials said.
Set up in 1992, the university now has 22,000 students.