A leading Derry dissident republican has been arrested by Gardaí in connection with the murder of former Sinn Féin official Denis Donaldson.
Gary Donelly, of the 32 County Sovereignty Movement - who is in his 40s - has been named locally as the man arrested in Clontibret, Co Monaghan on Saturday evening.
He is being questioned at Monaghan Garda Station under Section 30 of the Offences against the State Act, 1939.
This is the third arrest in relation to the ongoing investigation.
Mr Donaldson was shot dead at his isolated cottage in Co Donegal in April 2006, just months after publically admitting his role as a Special Branch and MI5 informer.
No-one has been charged over the 56-year-old's murder.