In a statement to the Irish News newspaper the New IRA offered "full and sincere apologies" to journalist Lyra McKee’s family and friends.
The 29-year-old reporter was shot dead in Derry, also known as Londonderry, last Thursday as she watched youths attack police following a raid.
Police said she was hit when a gunman opened fire in the direction of officers.
In a further development the Police Service of Northern Ireland (PSNI) announced Tuesday the arrest of a 57-year-old woman in connection with the shooting.
She was arrested under the Terrorism Act. Two people who had been detained were released without charge.
Ms McKee’s murder has been condemned across the political spectrum and by Church leaders.
Her killing comes 21 years after the Good Friday peace agreement was signed in Northern Ireland.
Lyra McKee's funeral will be held in Belfast on Wednesday.