Police in Londonderry have said they will co-operate with any investigation into weekend disturbances.
Equipment in a BBC marquee was damaged
They have rejected claims by Sinn Fein that its officers were heavy handed during trouble in the city.
Five officers received minor injuries and one civilian were hurt during the violence on Shipquay Street on Sunday.
Sinn Fein want the Police Ombudsman's Office to investigate the trouble. One man, who was arrested, has been released on bail.
Equipment, valued at thousands of pounds, was also damaged in a BBC marquee.
Local assembly member Martina Anderson said her party had been contacted by parents who claimed police had "assaulted" their children.
"The common belief is that a relatively minor scuffle between two individuals spiralled out of control following the intervention of a large number of PSNI personnel," she said.
Ms Anderson said that she condemned the rioting in the city, but "would not condone excessive force by the PSNI".
However, Chief Inspector Chris Yates said police run an operation in Derry city centre every Friday and Saturday night to stop assaults.
"This operation's been very successful over previous years and has reduced city centre assaults by over 50%," CI Yates said.
He said the officers were in the area "to stop fights and if they see a fight they're bound to intervene".
"Whatever's happened here, whatever the police are perceived to have done or not done, can never justify what we saw here on Sunday morning," he added.
"Bricks, bottles and paving slabs and fencing panels being thrown at police and thousands of pounds worth of damage done to property."
He said about 50 to 100 people were engaged in rioting although up to 300 were on the streets at the time.
Foyle DUP MLA William Hay said it was unacceptable behaviour.
"Every right thinking person across the city, irrespective of where they live, would condemn this," he said.
"Everybody believes we left this behind us and the city centre can be shared... there can be no excuse for it."
Police are examining CCTV footage of the disturbances.