Five men have been arrested by detectives investigating the murder of Constable Ronan Kerr in Northern Ireland.
Searches are under way in parts of Co Tyrone.
The new police recruit was killed by an under-car booby-trap bomb which exploded outside his house in Omagh, Co Tyrone, on April 2.
Constable Kerr was killed by dissident republicans opposed to the peace process in Northern Ireland.
He was one of a growing number of Catholic police officers joining the Police Service of Northern Ireland (PSNI).
It was one of the most serious incidents attributed to dissidents, who have also attacked police station and other security force targets.
Today, police said searches linked to the arrests were under way in Coalisland, Toome, Bellaghy and Ballyronan, Co Tyrone.