Police were attacked by loyalists after an un-notified loyalist protest parade in Co Tyrone at the weekend.
Petrol bombs and other missiles were thrown after the parade at Moygashel, near Dungannon, on Saturday.
A burning barricade was also placed across a road during the disturbances.
Police say one officer injured after being struck by masonry.
It has also been reported that police came under attack in the Sandy Row area of south Belfast on Friday; however, the disorder has been described as "minor".
Saturday's parade in Co Tyrone was the latest in a series held in loyalist areas in recent weeks.
Details of the event had been circulated on social media in advance.
It is understood that recent parades are part of the ongoing protest linked to the Northern Ireland Protocol, concerns over last year's Bobby Storey funeral and claims of two-tier policing.
Footage of Saturday night's parade appears to show bandsmen, some who were masked, parading to police lines where the road was blocked by PSNI Land Rovers.
Under the law all public processions are supposed to be notified to the Parades Commission.
Chief Inspector Tim Flanigan said the Moygashel parade, which formed at around 8pm, was un-notified and that "officers administered warnings to participants and put an evidence-gathering operation in place".
The trouble continued to around 11pm when the crowd dispersed.
Mr Flanigan added: “We will now review all the evidence gathered to identify those responsible for the disorder and any other offences which may have been committed.”
