NEW : One officer was injured in a third night of violence in Belfast . NEW : About 150 people fired shots and threw stones at officers . NEW : Police are now trying to arrest those involved . `` Over 80 police officers have been injured after being attacked , including by petrol bombs , pipe bombs , and bricks , '' Cameron said . NEW : Prime Minister David Cameron denounced ` ` unacceptable '' violence .
NEW : One officer was injured in a third night of violence in Belfast . NEW : About 150 people fired shots and threw stones at officers . NEW : Police are now trying to arrest those involved . NEW : Prime Minister David Cameron denounced ` ` unacceptable '' violence .