BELFAST  - Seven police officers were injured in Belfast after being attacked with petrol bombs in a second night of violence by Protestant rioters in the Northern Irish capital, a spokeswoman said Sunday. Bricks, bottles, furniture and other missiles were also hurled on Saturday night by hooded youths, some with British flags covering their faces.

The seven injured officers did not require hospital treatment and remained on duty, a spokeswoman for the Police Service of Northern Ireland (PSNI) said.

Police used water cannon and fired baton rounds, although the unrest was not as intense as on Friday night, when 32 officers were injured and a leading politician was knocked unconcious by a brick. Twenty-two people were arrested on Friday after crowds attacked police with petrol bombs, sticks, fireworks, bricks, bottles, masonry and even a sword.

 Another 11 arrests were made overnight Saturday.

About 1,000 police officers from mainland Britain were sent to Northern Ireland in anticipation of tensions over the traditional Twelfth of July parades, the pinnacle of the Protestant Orange Order's marching season.

Trouble flared Friday after police tried to enforce a decision by an adjudication body banning the Orange Order from marching through a Catholic republican area of Belfast.

"The scenes were both shameful and disgraceful," Chief Constable Matt Baggott of the Police Service of Northern Ireland (PSNI) told reporters on Saturday.

He criticised leaders in the Orange Order who had called for protests against the decision to block their march through the republican Ardoyne area, saying they had been "reckless".

Nigel Dodds, the member of parliament for North Belfast, was taken to hospital after being hit on the head with a brick while trying to calm the crowds down on Friday night. He was later discharged.

The July 12 parade marks the victory of Protestant king William III of Orange over the deposed Catholic king James II at the Battle of the Boyne in 1690.

It is a flashpoint for tensions between the Protestant and Catholic communities in the province, which was devastated by three decades of sectarian violence in the 1970s, 1980s and 1990s.

The 1998 Good Friday peace accords largely brought an end to the unrest, known as The Troubles, although sporadic violence and bomb threats continue.