There has been revulsion at the murder of Lyra McKee
Dublin (AFP) - 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".
- Brexit fuels the fire -
McKee's murder follows a car bomb in Londonderry in January and a spate of letter bombs sent to British targets in March -- both claimed by the New IRA.
There is speculation that Brexit -- which has raised the spectre of a hard border between Ireland and Northern Ireland -- is acting as an irritant to dissident republicans.
Proposed divorce deals with the EU could see Northern Ireland more closely aligned to the Republic of Ireland or bound tighter in union with mainland Britain -- raising competing loyalist and republican visions of the future.
Kieran McConaghy, a lecturer in terrorism at the University of St Andrews in Scotland, said it was "hard to say" whether Brexit has played a "major role" in recent attacks, as such events have been consistent since the ceasefire.
Since the British government began publishing security assessments in 2010, the threat of terrorism in Northern Ireland has remained at "severe" -- denoting that an attack is considered "highly likely".
However, "Brexit hasn't been good for stability in Northern Ireland", McConaghy told CBC.
"It has made people more uncomfortable with the peace process in Northern Ireland, which is seen to be faltering at present.
"Politicians would do well to try and clarify some of the uncertainty... so that organisations like the New IRA and others don't fill that political vacuum."
There are particular fears that a no-deal hard Brexit would see checks erected along the 500-kilometre (310-mile) border, which would offer dissident militants a natural target.
- Sea change -
Following McKee's murder, police in the republican area of Londonderry where McKee was killed say they have experienced a "sea change" in previously-strained community attitudes towards officers.
The Free Derry Corner landmark wall has been repainted to reflect the local community's revulsion.
Underneath the sign "You are now entering free Derry", marking the start of a republican area, a message now reads: "Not in our name. R. I. P. Lyra."
In the wake of her murder, Northern Ireland's six main political parties -- including rival unionists and republicans who have been unable to form a devolved government for more than two years -- issued a rare joint statement.
"It was a pointless and futile act to destroy the progress made over the last 20 years, which has the overwhelming support of people everywhere," it read.