Police investigating the murder of a prison officer in Northern Ireland have arrested two men.
Father-of-two David Black, 52, was shot dead as he drove to work on the M1 motorway in Co Armagh earlier this month.
The suspects, aged 34 and 42, were detained in Coalisland, Co Tyrone.
Mr Black, from Cookstown, Co Tyrone, was gunned down in a high-speed motorway ambush as he drove to start his shift at Maghaberry prison in Co Antrim.
The long-serving officer was nearing retirement.
A dissident republican group styling itself as the "IRA" claimed the murder.
Dissidents have been engaged in a long-running protest inside Maghaberry about jail conditions.
The arrests were made as it emerged the majority of inmates involved in the so-called dirty protest have ended their action. Around 30 prisoners had been refusing to wash and were smearing excrement on the walls and floor of their cells as well as emptying urine into the prison landings.
The protest, which started last May, was in opposition to strip searches. Around £500,000 has been spent cleaning the cells during the period.
The two arrested men have been taken to the Police Service of Northern Ireland's serious crime suite in Antrim. Four men have already been arrested and released in connection with Mr Black's murder.