Large crowds fled from police as they broke up a street party outside a block of student flats.
Officers were called to the University of Portsmouth's Margaret Rule Hall where they broke up the gathering at 0:46 BST.
Two hours later, the force had to disperse a group of 40 from the site.
Hampshire Constabulary said it had identified the organiser of the party and officers were reviewing footage of the gatherings on Isambard Brunel Road.
Police can issue £10,000 fines to the organisers of large gatherings, with attendees fined £200 for a first offence.
'Angry and disappointed'
Insp Marcus Kennedy said It was "frustrating" for officers forced to deal with "such a clear breach of the current restrictions" which had been "in place for some time".
"There is no excuse for this type of behaviour," he said.
University vice-chancellor Prof Graham Galbraith said he was "angry and disappointed".
He added: "I want to be clear that any student found to have broken the laws in place will face swift disciplinary action by the university as well as any fines that may be issued by the police."
There have been 306 new coronavirus infections recorded in the city in the the past week, with most in younger adults, and 1,390 positive test cases in total.