Two men aged 27 and 40 have been arrested in connection with the April 2011 murder of Constable Ronan Kerr.
The Police Service of Northern Ireland (PSNI) officer, 25, was killed by a booby-trap car bomb in Omagh, Co Tyrone, on April 2 2011.
A man aged 27 was arrested in Omagh and a 40-year-old was taken into police custody from prison.
The PSNI said: “Detectives from PSNI’s Serious Crime Branch today arrested two men under the Terrorism Act in connection with the murder of Constable Ronan Kerr in April 2011.
“A 27-year old man was arrested in Omagh and a 40-year old man was produced into police custody from prison.
“They have both been taken to Musgrave’s Serious Crime Suite where they are currently being questioned by police.”
Dissident republicans opposed to the peace process calling themselves the New IRA have been blamed for the attack on the Catholic new recruit outside his home.
The bomb was attached under his car and it exploded as he prepared to drive to work.
Constable Kerr was dubbed a “modern-day hero” by then PSNI chief constable Matt Baggott.
He was the second policeman killed after the PSNI was formed out of the Royal Ulster Constabulary in 2001.
He had joined the police in May 2010.