Police officers have been attacked by missile-throwing loyalists during fresh violence in Northern Ireland.

Youths attempted to hijack vehicles as a protest by up to 100 people turned violent in south Belfast.

Countless roads have been blocked across the city causing disruption to shoppers and commuters days before Christmas.

One police officer has been injured and the force has come under attack from missile throwers in the Lower Newtownards Road, Sandy Row and Shaw's Bridge areas. Several hundred people were involved.

Around 200 people were involved in the disorder on the Newtownards Road.

Some retailers said their businesses had been devastated by a campaign which has continued since the start of the month, following the reduction in the number of days the Union flag can be flown from Belfast City Hall. First Minister Peter Robinson and Deputy First Minister Martin McGuinness have appealed for the protests to stop.

Earlier on Monday Northern Ireland Secretary Theresa Villiers met leaders of the province's main political parties to discuss the flags controversy.

"I have today urged Northern Ireland's political leaders to come together to find a way forward to resolve the ongoing protests on flags," she said.

"It is vital that all the parties work together to make progress towards a cohesive and shared society where decisions on issues like flags can be made in a way which respects different views and takes into account the different traditions and identities of modern Northern Ireland."

She said she understood the strength of feeling but the disruption caused by these protests was damaging Northern Ireland's economy, particularly for retailers heavily dependent on shoppers in the run-up to Christmas.