Belfast protests: Police arrest more than 40 people
11 December 2012 Last updated at 15:41 GMT
Police in Belfast say they are treating an attack on one of their patrol cars as attempted murder.
A gang of masked men threw a petrol bomb into the unmarked vehicle while a police officer was inside.
Loyalist protesters are angry about a decision by Belfast City Council to restrict the flying of the Union flag.
The Alliance party, blamed by some Loyalists for not blocking the move, says protesters also attacked one of their offices at Bangor in County Down with petrol bombs.
Assistant Chief Constable George Hamilton, from the Police Service of Northern Ireland, said more than 40 people had been arrested.