Four police officers have been injured during significant disorder following an Orange Order parade in North Belfast.
The loyal order march through the Ardoyne sectarian interface was peaceful but trouble flared nearby with crowds of several hundred confronting lines of riot police.
Fireworks, petrol bombs, stones, bricks and bottles were hurled at police lines and a burning silver BMW driven at officers in the residential neighbourhood of red-brick terraced houses.
A republican march through the same area shortly afterwards prompted an exchange of missiles between loyalists and nationalists.
Water cannon vehicles were used extensively and one non-lethal baton round fired.
Police Service of Northern Ireland Assistant Chief Constable Will Kerr said: "Unfortunately, police are now dealing with significant disorder in the Brompton Park and Balhom Road area.
"Water cannon has again been deployed and four officers have been injured. Their injuries are not believed to be life- threatening.
"I am urging all individuals and communities affected to respond to developing events in a calm and responsible manner. Violence has serious and unwanted consequences for us all and we will robustly investigate all incidents of disorder."
Other Orange parades across Northern Ireland passed peacefully.
A token parade by around 15 Orangemen through Ardoyne passed in silence just before 4pm. A residents' protest supported by Sinn Fein was peaceful.
Democratic Unionist MP Nigel Dodds said the second march by nationalists was linked to dissident republicans.
He criticised the Parades Commission's decision to allow the republican parade.
"The Parades Commission pandered to this outfit. They are incapable of reaching a resolution because they only want violence, they don't want settlement, they just want to derail the peace process," he said.
Police appealed for calm in the area.
The Protestant Orange Order is marking the Twelfth of July culmination of its summer marching season, with many parades across the region. It celebrates the victory of Protestant King William over Catholic King James.
Ardoyne has been the scene for trouble on this date for many years and has become a byword for intercommunal strife on that date, despite most people from the area disagreeing with violence.