Four police officers were injured during loyalist riots on the outskirts of the Northern Irish capital Belfast which continued into the early hours of Saturday.
Protesters threw petrol bombs, stones and fireworks at police and set fire to cars and one double-decker bus, while police used plastic bullets and water cannon.
The protests began six weeks ago when the local city council, which now has a stronger Catholic, pro-Ireland faction, voted to hoist the Union Jack only on designated days rather than every day.
Protestant loyalists see it as an attack on the region's belonging to the United Kingdom. Around 70 police officers have been injured and 100 people arrested in the protests.
Police said protesters blocked many streets, including several important roads, while according to the Belfast Telegraph a pipe bomb was found on one of the city's main roads.
Thousands of people left Belfast in order to avoid the riots, though one online counter movement launched a successful "sit-in" campaign in the city's pubs and restaurants, whose businesses have suffered because of the protests.