The killing of a journalist in Londonderry marks the latest upsurge of violence in Northern Ireland — where fears are growing that a fragile and hard-won peace is increasingly at risk.Lyra McKee, 29, was shot dead during a riot as dissident republicans clashed Thursday with police in the province’s second city — a historic flashpoint in the three decades of violence known as “The Troubles”. The 1998 Good Friday Agreement largely ended the turbulence in Northern Ireland — mandating a withdrawal of British security forces and the disarming of the Irish Republican Army (IRA) paramilitary group.But dissident republicans — seeking Northern Ireland’s departure from the United Kingdom and integration into the Republic of Ireland through violent means — remain active. Police believe the New IRA splinter group is behind McKee’s murder.Volatile fringe Among commentators there is a wide-held belief that the perpetrators are youngsters not old enough to remember “The Troubles”, and are being manipulated by a radical older element.“There’s a dangerous radicalisation of young people in Derry by those linked to and on the periphery of the New IRA,” wrote The Irish Times newspaper’s security correspondent Allison Morris. Police Service of Northern Ireland detective superintendent Jason Murphy, who is leading the probe into McKee’s death, warned: “What we’re seeing is a new breed of terrorist coming through the ranks.”Two men aged 18 and 19 were arrested Thursday but later released without charges. Police appealed again to the community for help in finding the killer.“I know there will be some people who know what happened but are scared to come forward but if you have information, no matter how small, please contact detectives,” said Murphy, stressing that the information would be treated as “100 percent anonymous”.