Nine police officers have been injured during an incident in north Belfast where the city's mayor had to be escorted by police away from loyalist protesters.
Sinn Féin's Máirtín Ó Muilleoir was brought to hospital following jostling and jeering at Woodvale Park.
The officers were injured when violent scuffles broke out at the official opening of the park.
A large crowd gathered in the area and missiles were thrown at officers as well as at Mr Ó Muilleoir.
Damage was also caused to his vehicle.
Police said the injured officers sustained cuts and bruising in what they described as "violent scuffles".
North Belfast Area Commander Chief Inspector Andy Freeburn said: "The PSNI will be investigating this appalling incident with a view to identifying those responsible."
"This should have been a positive day about the opening of a children's play park in the area, but instead was marred by disorder which has left a number of our community officers injured."
There were five nights of rioting in the Woodvale area last month following a Parades Commission decision not to allow the Orange Order make their return journey past the nationalist Ardoyne area on 12 July.