Who are the New IRA and what threat do they pose?
Video report by ITV News Correspondent Peter Smith
The New IRA has apologised for the murder of journalist Lyra McKee during a riot in Derry, Northern Ireland.
In a statement given to The Irish News using a recognised code word, the New IRA admitted responsibility, offering “full and sincere apologies” to Ms McKee's family and friends.
It said she was killed after volunteers were sent to "engage the enemy" - which it described as "armed British crown forces".
Friends and family condemned her death earlier this week, placed red paint hand prints on the office of an office of the paramilitary group in Derry.
Ms McKee's killing is not the first murder the group has been linked to in Northern Ireland, while it is also been blamed for several car bombs.
Who are the New IRA?
The New IRA are a group of dissident Republicans whose end game is to see British rule of Northern Ireland come to an end. It seeks a united island of Ireland.
The group is based out of Belfast but has members across the UK and Ireland. Its main strongholds of support are in Derry, Strabane, Lurgan and Co Tyrone.
It has been named a terrorist organisation because of the paramilitary tactics it uses to seeks its end goal. British security forces and Northern Irish police insist its numbers are limited, counting just a few hundred core members.
What is its relationship with the Real IRA?
The group's roots can be traced back to the mid-1990s when the Real IRA split after disagreements over a ceasefire.
It is thought between 2011 and 2012 the Real IRA - the group behind the 1998 Omagh car bomb - merged with several other groups to create the dissident group behind the shooting of Lyra McKee.
What other attacks has the New IRA carried out?
This year the group was responsible for a car bomb outside the courthouse in Bishop Street, Derry.
The explosives-laden car was left on the city centre street on a Saturday night in January, and scores of people, including a group of teenagers, had walked past before it detonated.
Whose murders is the group linked to?
It has been linked with four murders, including Pc Ronan Kerr, who was killed by an under-car bomb in Omagh in 2011.
The group is also linked to the deaths of prison officers David Black, who was shot as he drove to work at Maghaberry Prison in 2012, and Adrian Ismay, who died in 2016 after a bomb exploded under his van outside his home in east Belfast.
The New IRA also claimed a number package bombs posted to targets in London and Glasgow in March.
In its apology for the murder of journalist Lyra McKee, the New IRA claimed the shooting during a riot was an accident.
Who is the mouthpiece for the Real IRA?
It is represented by Saoradh, which states on its website it is "a new revolutionary party, organised across the Irish nation".
Saoradh releases media statements on behalf of the Real IRA, including when the group said it is behind the shooting of Lyra McKee in Derry. Its core message is to reject outside imperialism in Ireland and for the whole island to become a socialist state united under one flag.
What have other groups said about the Real IRA?
Following the death of Lyra McKee, DUP leader Arlene Foster tweeted the shooting was "a senseless act".
She added: "Those who brought guns onto our streets in the 70s, 80s & 90s were wrong. It is equally wrong in 2019. No one wants to go back."
On Easter Sunday, Sinn Féin leader Mary Lou McDonald said there was "no support" for armed action by the group.
She continued: "It is past time for these groups that masquerade as republicans to pack up."