Angry young men confront police in Northern Ireland on Saturday.

It's not unusual for the annual Protestant Orange Order marches in Belfast to turn violent.

The parades are a regular flashpoint for sectarian clashes.

A high profile peace deal in 1998 largely ended three decades of strife in Northern Ireland.

But Belfast is still riven with religious and nationalist tension between Protestants loyal to the British government and Catholics, many of whom favour reunification with Ireland.

The Protestant Orange Order was angered this year when authorities ruled they couldn't march a stretch of road dividing the two communities - an act seen as provocative by many in the Catholic community.

Police drafted 400 reinforcements from other parts of Britain as they battled Protestants demonstrators into the night.

More than 20 people have been arrested.