A bus bringing nationalists from a community festival to Crumlin Road jail in Belfast was pelted with eggs by a loyalist protest group.
Further rioting then broke out between loyalists and police reinforcements which were rushed to the scene.
Around 30 loyalists gathered outside the historic building to object to an event happening inside as part of the Ardoyne Fleadh last night.
Eggs were thrown at the bus carrying the group as it approached the jail as part of a pre-planned tour.
A Paratroop Regiment flag was also displayed by the protesters.
Among those being bused in was leading republican Eddie Copeland.
DUP MEP Diane Dodds was at the prison for a separate function and was caught up in the protest.
Police Land Rovers then moved into the area to try and prevent the situation getting out of control.
The protest subsequently ended and order was quickly restored.