Police investigating attacks on officers in County Antrim on Tuesday night are investigating whether there was loyalist paramilitary involvement.
Two officers were injured - one needed hospital treatment - in the violence in Carrickfergus and Ballyclare.
Two police cars were surrounded and attacked in separate incidents.
The PSNI have said one line of inquiry is an earlier police drugs operation at houses in the Castlemara estate in Carrickfergus sparked the disorder.
A small quantity of herbal cannabis and cannabis resin was recovered during the search.
A 37-year-old man allegedly caused a disturbance at the scene and was then arrested.
He was later charged with disorderly behaviour, criminal damage and resisting arrest and will appear in court next month.
Police came under attack by about 20 to 25 masked men during trouble in that estate hours after the operation.
Fireworks, bottles, bricks, paint and a number of petrol bombs were thrown at police vehicles which were in the area following reports of an assault.
One officer suffered minor injuries and a police vehicle was damaged.
In Ballyclare an officer suffered head injuries.
The officer was injured during a routine patrol in a police land rover in the Grange estate in the County Antrim town at about 2330 BST.
Petrol bombs were thrown by masked men and some vehicles were damaged.
The police officer was treated for head injuries but has been discharged.
There was also trouble in Eden, just outside Carrickfergus.
A number of youths blocked the road for a short time with burning wheelie bins.
South Antrim Ulster Unionist MLA Danny Kinahan described the attack on a police officer in Ballyclare as "totally unacceptable".
"I understand this was a routine police patrol - officers out checking on the safety of local residents when they were attacked by a group of people firing petrol bombs and lobbing stones and bricks."
"Let us be clear- these are gangs - gangs trying to assert some sort of authority and control in these estates.
"Their behaviour will not be tolerated however and I know the determined work the local community association has been doing to try and stop it.
"I would encourage anyone with information to come forward."
Newtownabbey Alliance councillor Tom Campbell also condemned the attack.
"I was shocked that a police officer who is there to protect our community was attacked in such a brutal manner.
"I hope that this officer is able to make a swift recovery from his injuries and that this attack will not deter him from serving our community."