The men in their 40s were arrested in Dublin and are being held in connection with the device discovered on June 1.
Gardaí (Irish police) arrested two men in Dublin on Tuesday morning in connection with a car bomb discovered under the vehicle of a police officer in Northern Ireland on June 1. The device was discovered under the police officer's car at Shandon Park golf club, close to Police Service of Northern Ireland (PSNI) headquarters in east Belfast.
The two men in their 40s were arrested by members of the garda special detective unit and are being held in a station in Dublin.
"The arrests should send a clear message to those involved in terrorist activity that the border does not provide an escape route," said Det Supt Sean Wright from the PSNI's terrorism investigation unit.
"Our two police services work collaboratively on a daily basis, sharing knowledge and information, to ensure that there is no hiding place for criminals or terrorists."
In June, the New IRA claimed responsibility for the attack in a statement to Northern Ireland newspaper The Irish News. The two men arrested Tuesday are being detained under Section 30 of the Offences Against the State Act at a Dublin Garda Station.
"Since the murderous attack on our colleague last month when terrorists placed an explosive device under a car, our investigation has continued at pace," Detective Inspector Anthony Kelly said of the investigation.
"Today's search and arrest operation is now complete and detectives are questioning two people arrested.
"We also seized a quantity of cash, electronic devices and suspected Class A and Class B drugs during one of the searches.
"We will continue to do everything possible within the law to bring those responsible to justice.
"We are working alongside the community to make this possible as we know there are people who know who did this and there are people out there who knew this was being planned.
"It was clearly intended to kill the police officer. But in placing this explosive device, the terrorists also put the lives of the officer's family, neighbors and members of the public at serious risk," Kelly added.
"Anyone who places an explosive device under a car in a built-up area after transporting it through local residential streets cares little about our communities.
"In stark contrast, they only care about themselves and their own selfish desires.
"Their violence is simply reckless and they cannot be allowed to continue to put communities in harm's way.
"Thankfully the violent dissident republicans' plan did not work but it does clearly demonstrate that they don't care who they attack or kill in the process."