Belfast, Northern Ireland: Violent clashes that engulfed Belfast city centre and left more than 50 police officers injured have been condemned as “mindless anarchy” by the province’s chief constable.

Police fired plastic bullets and water cannon after facing a barrage of missiles that left 56 officers injured during a second successive night of sectarian disorder. Matt Baggott, Northern Ireland’s chief constable, described the violence as “thuggery” and praised police for putting their lives on the line.

Tensions have spread elsewhere in Northern Ireland, with major controversy surrounding a planned Sinn Fin-backed commemoration event in the Co Tyrone town of Castlederg on Sunday for local IRA members killed during the conflict.

Michael Gallagher, who campaigns for victims of the 1998 Omagh bombing in which his son Aidan was killed, accused Sinn Fin of “double standards” for supporting the event which he said lauded two men who tried to blow up Castlederg in 1973.

“It is very sad that on all sides there is a ratcheting up of tension and worsening divisions by holding all these parades, whatever political persuasion they are,” he said. “I think it is double standards to say that you stand by the victims of the Omagh bomb but then praise the actions of others who wanted to bomb another town in Co Tyrone, or indeed anywhere in Northern Ireland.”

The latest outbreak of disorder erupted after crowds of loyalists gathered to oppose a planned republican parade on Friday evening along Royal Avenue, Belfast’s main thoroughfare.

When riot police moved in, they were hit with bricks, bottles, fireworks, metal guttering and beer glasses. A police spokesman said the crowd was “intent on creating disorder”, although some loyalists claimed police were heavy-handed. The march, which had received permission from the Parades Commission adjudication body, was to mark the introduction of internment without trial by the British authorities in Northern Ireland during the Troubles.

Eventually, the parade was forced to pass along a different route, moving into west Belfast after protesters were pushed back towards the Shankill area.

Four officers were taken to hospital and two civilians were reported to have been injured. Parked vehicles were set on fire in the nearby North Street area, while shops were damaged, including a bar. Seven people were held on suspicion of offences including riotous behaviour, disorderly behaviour and hijacking.

Two water cannon were deployed and 26 plastic baton rounds fired in an attempt to quell the violence.

Theresa Villiers, Britain’s minister for Northern Ireland, said: “The violence and attacks on police officers were shameful. Disorder on the streets is a hugely regrettable step backwards.”

Police mounted a major operation before the parade, involving hundreds of officers and dozens of vehicles. The Parades Commission had given permission for six loyalist protests against the march, although numbers were restricted to four.

The disorder came after eight police officers were injured during trouble at an anti-internment bonfire near the city centre on Thursday night. At one point, officers were attacked by a man wielding a sword. On the same night, a teenage boy and girl were stabbed at a bonfire.

Less than a month ago, parts of Belfast were consumed by rioting after Orangemen were prevented from parading past the nationalist Ardoyne area.

The violence came at a sensitive time for Belfast because it is hosting thousands of international visitors attending the World Police and Fire Games.

Nelson McCausland, Democratic Unionist North Belfast MLA, said: “What should have been a great week for the city has ended badly and the image of Northern Ireland has been tarnished by violence.”