Media playback is unsupported on your device Media caption The BBC's Andy Martin said youths hijacked a bus and drove it at police lines

Twenty-two police officers were injured during rioting in Belfast on Monday night.

A bus was hijacked and driven at police during the disturbances ahead of the annual Twelfth of July celebrations.

Crowds of nationalists also threw petrol bombs and masonry at police during serious rioting in the west of the city.

Fifty-one plastic bullets were fired in response by police in the Broadway and Oldpark areas.

More than 40 petrol bombs were thrown at police, who said crowds of about 150-200 people were involved in the violence at Broadway and about 200 in both the Oldpark and New Lodge areas of north Belfast.

A number of arrests were made.

Police said an ambulance crew was attacked whilst they attended a hoax call in Brighton Street off the Falls Road.

A fire engine had its windscreen smashed by youths throwing bricks and bottles whilst attending a fire at the side of the Glen Road in west Belfast.

Police are investigating reports that gunshots were fired at Broadway at about 0115 BST. There are no reports of any injuries as a result.

While four officers received hospital treatment, none of the injuries are believed to be life-threatening.

Analysis The sight of 60 brand-new armoured police Land Rovers on the streets of Northern Ireland shows how precarious the security situation remains. It demonstrates how violence - albeit on a much reduced scale - is still part of life in some areas. Armoured vehicles used during the Troubles were due to be phased out by now. Belfast was supposed to have the same type of police cars as Blackpool, Bridgend and Brechin. The 60-strong new fleet of armoured vehicles is facing a baptism of fire this week.

In Portadown, two police officers were injured in rioting near Obin Street in the town.

On the Twelfth of July, the Protestant Orange Order takes part in demonstrations across Northern Ireland, commemorating Prince William of Orange's 1690 Battle of the Boyne victory over catholic King James II.

'Havoc'

On the Falls Road, in the west of the city. A driver was dragged from his bus and the passengers ordered off.

It was then driven at police lines on Donegall Road, but crashed a short distance away. A van was also set alight on the Donegall Road.

Assistant Chief Constable Dave Jones praised his officers for their "skill and professionalism" in dealing with the violence.

"Unfortunately 22 officers sustained injuries while delivering this protective service," he said.

"We would appeal for everyone to do everything they can to help ensure all areas are calm and peaceful over the next 48 hours. Violence does not need to be inevitable."

Sinn Fein MLA Jennifer McCann was at Broadway for several hours during the trouble. She believes that those taking part in the rioting were not from the area.

"Mostly what I saw was people who came from other parts of Belfast, who would be known as anti-social elements, who had taken a lot of drink and were attacking the police," she said.

Image copyright (C) British Broadcasting Corporation Image caption Debris from rioting still smouldered on Broadway on Tuesday morning

"The only people that they were causing havoc to, apart from the PSNI, last night, were local residents.

"Children were terrified in their homes, people fearful that their cars might be hijacked, people fearful that their homes might be attacked.

"What I witnessed last night was a disorganised mob attacking police lines."

Street violence

Police used water cannon after coming under attack from a crowd of up to 200 people throwing missiles and stones in the Broadway and Falls Road areas.

About 40 people gathered in North Queen Street and petrol was thrown at police.

There was also trouble in north Belfast.

There was a minor disturbance on the Shore Road after a barricade was erected across the road at Greencastle Station. It has now been removed.

There were also minor disturbances in the Whitewell area of the city.

A number of residents in the Ballysillan area have had to leave their homes because of a security alert.

A local community centre was opened to accommodate them.

Army bomb experts were called to examine a suspicious vehicle at Glenbryn Parade, but the incident was later declared a hoax.

The Northern Ireland Fire and Rescue Service (NIFRS) said one firefighter was slightly injured by youths throwing stones in Londonderry.

It said it was dealing with around one call every 75 seconds across Northern Ireland. By 0100 BST on Tuesday it had received 180 fire calls, a 65% increase on the previous year.