More than 20 police officers have been injured following overnight disorder in Portadown.
Officers came under sustained attack with heavy masonry, fireworks and beer kegs in the Co Armagh town on Thursday night.
A police spokesperson said 22 officers were injured and two people were arrested.
A woman aged in her 50s and a man in his 30s were arrested on suspicion of riotous behaviour and other offences in connection with the disorder.
The latest incidents followed three consecutive nights of violence, mainly in Ballymena, Co Antrim which followed a protest over an alleged sexual assault.
There was also sporadic disorder elsewhere in Northern Ireland on Thursday night following mainly peaceful protests, including in the Templemore Avenue area of east Belfast, where bricks were thrown through the windows of two houses in Avoniel Road in what police have termed a racially motivated attack.
A small fire at the Manse Road roundabout in Newtownabbey was also reported, and anti-immigration hate graffiti is being investigated in Newtownards.
Meanwhile, a house fire in the Mount Street area of Coleraine which led to the evacuation of a family with three young children, is being treated as deliberate and a racially motivated hate crime.
Police Service of Northern Ireland Chief Constable Jon Boutcher warned on Thursday his officers would be coming after the “bigots and racists” behind the disorder.
He also said that the young girl who was the victim of an alleged sexual assault in Ballymena at the weekend had been “further traumatised” by the rioting across the week.
In a statement on Friday morning, Assistant Chief Constable Ryan Henderson said police had come under sustained attack in Portadown.
“Officers deployed a variety of public order tactics to restore order to the town as quickly as possible,” he said.
“Twenty-two officers were injured and I am so grateful to them for their bravery and selfless dedication in protecting the community of Portadown from this criminality.
“We saw calm in Ballymena and I hope the powerful words of the family who asked for calm during this really difficult time were heard and continue to be heard over the coming days.”
He warned that while two arrests have been made so far in terms of the disorder in Portadown, more will follow.
“I repeat, once more, our appeal for calm across Northern Ireland in the coming days,” he said.
By Thursday, 41 police officers had been injured, with 15 arrests.
