Two police vehicles have been damaged during disorder in Londonderry.
A police spokesperson said officers in the Creevagh Heights area of Derry “came under attack” from a number of youths.
Items including stones and bottles were thrown at officers causing damage to two police vehicles.
The Creevagh Road, country-bound, was closed on Friday night during the scenes.
Superintendent Claire Hamilton described “completely unacceptable behaviour”.
“Officers who were present in Creevagh Heights today, as part of an ongoing policing operation, have come under attack this evening from a number of youths, who gathered earlier this evening and began making threats of violence towards police,” she said.
“Some of the youths were wearing masks, some were also armed with weapons, while some had tins of paint and fireworks. They subsequently proceeded to throw items, including stones and bottles, at officers, causing damage to two police vehicles.
“This is completely unacceptable behaviour – attacking officers while they’re performing duties to protect the public – and we know it is not welcomed by the wider community.”
Ms Hamilton said a public safety operation remained in place late on Friday night.
“We would appeal to those engaging in this behaviour to refrain from doing so as our policing operation continues,” she said.
“Our officers are also engaging with local community reps this evening and we would reiterate our appeal for calm.”