Garda Commissioner Martin Callinan has said there are 25 organised criminal gangs operating in the State.

Speaking at the Oireachtas Justice Committee, he said the majority of the gangs are based in Dublin, Cork, Limerick, Galway and Sligo.

The commissioner said a number of the gangs have a significant international dimension and some interact to pursue joint enterprises.

The majority are involved in drug-trafficking and are prepared to use violence and intimidation.