Students could face disciplinary action and a curfew over coronavirus breaches, the University of Manchester has said.
The university said it was giving "active consideration" to reports of social distancing breaches at halls of residence in Fallowfield.
It said students could face expulsion if they do not adhere to restrictions.
The National Union of Students (NUS) said there would always be rule breakers, but "we need to be very careful not to scapegoat young people".
Thousands of students have arrived in the city over the past week for the start of the new term.
About 8,000 of the university’s 40,000 students live in its 19 halls, seven of which are in Fallowfield.
Coronavirus restrictions in Manchester currently mean people cannot mix with those from outside their household or support bubble.
In an email to students, the institutions said police were called to "significant breaches" over the weekend and issued fixed penalty notices.
Greater Manchester Police have been approached for comment.
The university's spokesman said it had been "very clear to students that they must respect social distancing rules and all other restrictions to keep themselves and others safe".
"Additional security officers have been deployed in Fallowfield and further reminders sent," he said.
"If students do not comply, they will face disciplinary action, which could lead to expulsion, and we will not hesitate to involve the police."
He added that a number of "offending students" would now be disciplined using the university's procedures and "active consideration is also being given to introducing a curfew across all halls".
"We really want to avoid this, but if residents fail to adhere to social distancing rules we will be faced with no alternative."
The NUS said all universities had "procedures in place to deal with misconduct and these are appropriate to be able to deal with any rule breaches".
"As with any part of society, there will be people who break the rules, but we need to be very careful not to scapegoat students and young people.
"Not only would this be inaccurate and unfair, it also creates a culture of mistrust... when what we actually need is to build a culture of collective care."