According to an Irish newspaper, the New IRA has given responsibility for the murder of 29-year-old journalist Lyra McKee.
In a statement given by The Irish News with a recognized codeword, the group apologized "bluntly and sincerely" to their family and friends.
Ms. McKee was shot in the head while watching rebellions on Londonderry's Creggan Estate Thursday night.
The New IRA said it had been killed "alongside the enemy forces."
- Journalist shot dead in Derry riots
- "Massive" public reaction to murder of McKee
In a statement to the Irish News acknowledging responsibility for the killing, the Republican dissident group said, "During the attack on the enemy, Lyra McKee was tragically killed when
The group offered "their full and sincere apologies to their partner, family and friends of Lyra McKee for their death".
The group also accused the police of "provoking" the upheavals that preceded the weapons attack that killed Ms. McKee.
"On Thursday night, following a raid on the Creggan by heavily armed British Crown Corps that led to unrest, the IRA sent our volunteers to get involved," she said.
It added that it has "instructed our volunteers to use the utmost care in the intervention of the enemy in the future and to take measures to ensure this".
The statement comes after the leftist Republican political party Saoradh – backed by the New IRA – had previously tried to justify the use of force on Thursday.
Ms. McKee was standing near a police 4×4 police car when she was shot after a masked gunman shot at police and spectators.
On Monday, a protest by friends of Ms. McKee took place in front of an office in Derry used by Republican factions.
A number of women smeared red hand prints on republican slogans outside the office.
The police were present but did not make an immediate arrest.
The police said the public response to the murder had been "massive."
Det Supt Jason Murphy said there had been a "tangible change" in the sense of community to support her investigation, in the form of classified information.
He has called on members of the public to "step forward and talk to me."
It is assumed that the police and prosecutors have discussed what action might be possible to protect witnesses who are afraid of bringing evidence to court.
The New IRA is the largest of the dissident republican groups operating in Northern Ireland.
The group was linked to four murders and formed between 2011 and 2012 following the merger of a number of smaller groups, including the Real IRA.
The New IRA also called for a series of packet bombs shot down in London and Glasgow in March.
The murder of Ms. McKee took place 21 years after the signing of the Good Friday peace agreement in Northern Ireland.
The 1998 peace agreement marked the end of a decade-long violent conflict known as the Troubles, involving Republicans and loyalists. During this time, an estimated 3,600 people died.
The Good Friday Agreement was the result of intense negotiations between the British and Irish governments and the political parties of Northern Ireland.
Ms. McKee's funeral will be held on Wednesday at St. Anne's Cathedral in Belfast.
Her partner, Sara Canning, said the service was a "celebration of her life".