Riot police were pelted with bottles, fireworks and a smoke bomb yesterday as drunken young people flooded Belfast city centre to celebrate St Patrick's Day.
A boy of 15 was one of at least four people arrested on suspicion of disorderly behaviour or assault.
Large crowds of drunken young people were also reported in the Holylands area of Belfast last night – the scene of serious rioting in previous years.
But during the day confrontations took place between young people draped in Irish tricolours and the PSNI at Cornmarket, Ann Street and Castle Street.
Shoppers and tourists were left terrified as riot police formed lines on Ann Street at around 4pm in an attempt to clear the city centre of the hundreds of teenagers, many of whom were clearly drunk.
DUP councillor Gavin Robinson said many shops appeared empty and that there were scores of young people – who had clearly taken too much drink – "running amok".
He told the Belfast Telegraph: "The scenes were bound to have had a serious impact on trade."
DUP group leader on Belfast City Council Lee Reynolds said he was concerned by the reports of disturbances.
He added that this was the second year in a row that there had been trouble at the parade.
"I will be asking police for information about the disturbances," he said.
"There has been issues at this event for the second year in a row, there needs to now be an examination about this event."
There was also a brief clash between St Patrick's parade spectators and loyalists at Belfast City Hall.
Protesters who regularly demonstrate at City Hall against the reduction in the number of days the Union flag is flown, turned out yesterday – a statutory day during which the flag flies.
Sinn Fein councillor Caoimhin Mac Giolla Mhin accused flag protesters of harassing and verbally abusing people, including young children, attending an Irish language celebration at City Hall.
"The St Patrick's Day event inside City Hall hosted by Belfast Mayor Mairtin O Muilleoir to celebrate the city's diverse Irish language community was a huge success," he said.
"It was positive, respectful and inclusive of all the city's burgeoning Irish language community.
"It recognised the contribution of a range of individuals in promoting Irish and Irish culture in a positive pluralist fashion right across the city.
"The flag protesters outside, on the other hand, were very provocative and some of them harassed and verbally abused people, including young children, on their way into City Hall."
He claimed: "Some of the protesters then tried to get in to City Hall in an effort to disrupt the cultural celebration."