Three men have been arrested by police investigating a claim of responsibility for the shooting of senior detective John Caldwell.
The trio, aged 23, 25 and 36, were arrested in Derry under the Terrorism Act.
They have been taken to Musgrave Serious Crime Suite in Belfast for questioning.
An attempted murder investigation was launched by police after Detective Chief Inspector John Caldwell was shot several times at a sports complex in Omagh in February.
Dissident republicans are suspected as being responsible for the attack.
A typed message, purportedly from the New IRA, was posted on a wall in Derry and said the group was responsible for the shooting.
The senior detective spent several weeks in intensive care following the incident.
He was seen in public for the first time following the incident at a garden party at Royal Hillsborough in May, during a visit by the King and Queen, where he had a private audience with Charles.