The military-backed authorities in Bangladesh have detained five senior academics after anti-government rioting on campuses across the country.
They have also been raiding buildings across the capital, detaining students on suspicion of involvement in three days of rioting earlier this week.
A curfew imposed in Dhaka and five other cities was lifted for most of Friday but is now back in force.
One man has died in the protests, which are over continuing emergency rule.
The demonstrations have been held in defiance of a ban imposed under the state of emergency, which has been in place since January.
Two of those detained were senior academics in the capital.
Anwar Hossain, secretary of Dhaka University's teachers' association, and Harun-Or Rashid, the dean of the university's social science faculty, were taken into custody by army-led forces in raids on their homes on the university campus.
They are both accused of having been active in the protests.
Mr Hossain's son, Sanjeev, told the BBC: "My father was pretty much calm, and he wanted to know the grounds on which he was being taken away.
"They said that they did not know because they weren't very high officials, they were just performing their duties."
He added: "But they also said that there was nothing to worry about - that's what they always say - and when we asked them when he would be returned, they said that they did not know."
In the north-western city of Rajshahi three other academics are also being held by police.
Two men, Saidur Rahman Khan and Abdus Sobhan, are suspected of instigating violence in which one man died earlier in the week, the head of the city's university, Altaf Hossain, said.
"Their families said security forces in civilian dress picked up the teachers from their homes," he told the AFP news agency.
Later on Friday, a third academic, Malay Bhowmik, was also detained in Rajshahi.
The BBC's John Sudworth in Dhaka says that as police left one address during their investigations, two men were found who appeared to have been seriously beaten.
Discontent has been rising recently over the cost of living
Furthermore, two television stations have received visits from the censors warning them not to criticise the government.
Two previous Bangladeshi military governments have been felled after protests started by students.
As well as the man who died in Rajshahi, several hundred were hurt in the capital and elsewhere during the riots.
Violence has subsided in the past couple of days.
Monday's clashes began when students in Dhaka said they had been "manhandled" by soldiers during a football match. The unrest later spread across the country.
A curfew was imposed on six cities on Wednesday night. It was briefly lifted on Thursday and the government lifted it for 14 hours, from 0800 to 2200 (0200 to 1600 GMT), on Friday.
The interim government took power in January, when elections were cancelled following months of violence.
The administration initially enjoyed widespread popular support, as it promised to stamp out corruption and to hold elections by the end of 2008.
But discontent has been rising in recent months, most notably over the increasing cost of living.