Two people were arrested following clashes in the centre of Belfast after a day of St Patrick's Day celebrations.
A teenager was taken to hospital with facial injuries after violence involving around 30 people in rival groups battling with hurley bats and sticks last night close to St Anne's Cathedral in Donegall Street.
His injuries were not thought to be life-threatening.
A 16-year-old youth and a 25-year-old man were arrested on suspicion of causing grievous bodily harm and possession of offensive weapons, said a police spokeswoman.
She said the clash was not believed to have a sectarian motive and calm had been restored.
The trouble was only a short distance from where up to 5,000 people attended a free open-air concert following the St Patrick's Day carnival parade through Belfast city centre.
Also last night a 15-year-old youth was injured in a gang attack at a shopping centre in the border city of Newry, Co Down.
Both his hands were slashed in the attack by up to six youths at the Buttercrane Centre said police.
One of the attackers was armed with a knife and another with a Samurai sword - although the victim did not suffer knife wounds.
A police spokeswoman said the assault appeared to be a totally unprovoked and appealed for anyone who witnessed what happened to contact them.
Meanwhile a 19-month-old child was in the back of a car seized by hijackers in Belfast last night.
The vehicle was hijacked in the Mays Meadow area of the city a short distance from the Waterfront Hall and driven across the Albert Bridge into east Belfast.
Police said the silver car was found abandoned a short time later in the nationalist Short Strand area and the child, unharmed, was reunited with its distraught parents.
The hijacking may have been linked to disturbances caused by youths in the Short Strand area, said police, who appealed for any witnesses to the incident to contact them.