Denis Donaldson: Donegal arrest over 2006 killing
Irish police have arrested a man in connection with the murder of a former Sinn Féin official and republican informer.
Denis Donaldson was murdered in County Donegal in April 2006, months after being exposed as an agent who worked for the police and MI5 for 20 years.
He was once a key figure in Sinn Féin's rise in Northern Ireland politics.
A man in his 40s is being held at Letterkenny Garda Station in County Donegal.
He was arrested at Cloghercor in Doochary, County Donegal, on Thursday.
Last month, 74-year-old man appeared in court in Dublin accused of withholding information about Mr Donaldson's murder.
Mr Donaldson, 55, was shot dead at an isolated cottage near Glenties.
His family took legal action against officials in the Republic of Ireland in April after an inquest into his death was adjourned for the 19th time.