Two men are facing extradition to the North in connection with the murder of an RUC officer in the 1970s.
The men, aged 73 and 72, were arrested by Gardaí in counties Meath and Donegal this morning.
Police in the North say the 72-year-old is wanted on suspicion of murder.
The 73-year-old is wanted on suspicion of firearms offences and attempted murder.
RUC Constable Robert John McPherson was killed after being called to reports of suspicious activity at a post office in Dungiven in County Derry on July 26th, 1975.
The Provisional IRA later claimed responsibility.
A Police Service of Northern Ireland (PSNI) spokesperson said the men were arrested by Gardaí under a Trade and Co-operation Agreement (TaCA) Warrant as part of a joint operation.
One of the men is due to appear before the High Court in Dublin this morning, while the other is due to appear this afternoon.
A third man (71) has been arrested by PSNI detectives in the Dungiven area of County Derry as part of the same investigation and is due to appear in court later today.
“The Police Service of Northern Ireland has been liaising closely with An Garda Síochána and today’s arrests demonstrate the benefits of joint working between police services and other national partner agencies,” said the spokesperson.
The PSNI said the decision to prosecute the three men was issued before the UK’s controversial Northern Ireland Troubles (Legacy and Reconciliation) Act came into force at the start of May.
The act, which is being challenged by the Irish Government at the European Court of Human Rights, will end most legal proceedings linked to legacy cases.