Violence has erupted in Northern Ireland between pro-Britain Protestants and pro-Ireland Catholics, leaving two people with gunshot wounds.

Police said Tuesday hundreds of people were involved in the disturbances, the largest breakout of violence after a long period of peace between the two factions.

Rioters Monday night pelted homes with fire bombs, bricks and stones in the Short Strand Catholic area before shots rang out and police moved in.

It was not clear what sparked the attacks, but the outbreak comes at the start of annual sectarian parades.

Protestant and Catholic factions in Northern Ireland reached a power-sharing agreement in 1998 that largely defused decades of violence in which 3,500 people died.

A report released Tuesday by the Historical Enquiries Team, which investigates incidents during the so-called time of “The Troubles,” concluded that in 1976, the Provisional Irish Republican Army lined up and executed 10 Protestant workers.

The Provisional IRA denied responsibility for the massacre.