Police are working to identify those involved in the public disorder in Londonderry on Friday night.
Two police vehicles were damaged during an ongoing policing operation in the Creevagh Heights area when young people, some of whom were masked and armed with weapons, threw stones and bottles at officers.
Police said that no injuries were reported and crowds dispersed at about 23:30 BST.
Superintendent Claire Hamilton said: “An investigation has been launched, and evidence gathered last night will be reviewed in order to identify those involved.”
She added: “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.
“Our engagement with local representatives around these issues is ongoing as we work to keep everyone safe, including our own officers who continually put themselves in harm’s way to protect the community.”