Police in Northern Ireland have been given a further six days to question two men over the murder of constable Ronan Kerr.
The men, aged 26 and 40, were arrested last week.
Detectives are also questioning a 33-year-old man in connection with the booby trap bomb that killed the 25-year-old Catholic officer in Omagh on April 2.
Dissident republicans opposed to the peace process were blamed for the device that exploded under the policeman's car in the Co Tyrone town.
The same extremist groups are believed to be behind a 500lb van bomb police discovered near the border city of Newry, Co Down, last Thursday.
On Sunday a peace rally in Omagh attracted support from across the community and was attended by friends and relatives of the murdered officer.
While the march was not party political, organisers said it was intended to send a message of support in the peace process.