Police officers are monitoring social media to disrupt plans by gangs of teenagers for mass fights and drunken parties at locations across Belfast.
Teenagers are increasingly using social media to arrange violent clashes or large social gatherings, police have warned.
One of the largest pre-planned fights witnessed by police to date took place on Saturday evening, when around 100 youths gathered in Belfast city centre.
Several teenagers were arrested and others cautioned after officers disrupted youths gathering to fight at around 10.30pm in the city's main shopping area.
A vehicle was damaged as the crowds made their way through Cornmarket and out to Castle Place. Two males, aged 15 and 16, were arrested on suspicion of riotous behaviour and criminal damage. The previous evening two girls, aged 14 and 15, were cautioned following reports of a planned fight.
"You only have to look back at other incidents and see that one punch can be fatal. My message to these young people is do not get involved and do not go along as a spectator. You are putting your future at risk by taking part in this type of thing," said north Belfast commander, Chief Inspector Bobby Singleton.
He added: "Getting caught up in this type of criminal behaviour can result in a criminal record, which is damaging to future career prospects." Mr Singleton said that some of the arranged fights have been sectarian in nature, but others have been related to arguments over girls and other issues.
It is not just prearranged violence that is of concern to police. Teenagers have been using social media to organise large parties and social gatherings in public places.
In recent weeks, more than 300 young people gathered at Cavehill Country Park for a party. "Luckily, neighbourhood officers were able to disperse the crowd without incident. When large numbers of young people come together there is a safety risk, especially somewhere like Cavehill Country Park, which was closed to the public at the time and was in darkness. There is also the risk of anti-social behaviour, drugs and alcohol," Mr Singleton said.
He added: "We will continue to monitor social media and work with local communities to stay ahead of this."