(CNN) -- Hundreds of additional police officers are being sent from Britain to Northern Ireland on Saturday after a night of loyalist rioting in Belfast left 32 officers injured across the city, police said.
Officers came under attack Friday evening in north Belfast, the Police Service of Northern Ireland said, as loyalists protested a decision to bar a Protestant Orange Order march from returning through the mainly nationalist and Catholic Ardoyne area.
Police footage posted on YouTube showed an angry crowd, with men wielding batons and throwing projectiles after police vehicles blocked their way. Police deployed water cannon in response.
Lawmaker Nigel Dodds was briefly hospitalized after being struck on the head with a brick or a bottle thrown at police, authorities said.
Trouble also broke out in south and east Belfast, leading to the arrests of seven men.
Chief Constable Matt Baggott described the night's rioting as "shameful and disgraceful."
He said that another 400 police officers would arrive in Northern Ireland from Britain on Saturday as backup in case of further disorder.
More than 600 "mutual aid" officers from Britain are already in Northern Ireland to support local police.
The Orange Order said early Saturday that it was suspending the protests it had called over the route the marchers were allowed to take Friday in north Belfast.
The route was decided by the Northern Ireland Parades Commission, which rules on which marches are allowed to take place and which are banned, in an effort to keep friction to a minimum.
July 12 is an important day for marches because it celebrates Protestant William of Orange's defeat of the Catholic King James II at the Battle of the Boyne in 1690.
Hundreds of parades take place across Northern Ireland each year, the majority involving the Orange Order and associated organizations, although pro-Irish nationalists also have marches.
Most parades pass off peacefully, but when members of one community march near or through neighborhoods dominated by another, violence sometimes results.