Derry councillor Gary Donnelly has been arrested in connection with the 2006 murder of British agent Denis Donaldson.
Mr Donnelly, who was previously a spokesman for the dissident republican 32 County Sovereignty Movement, was arrested as he left a commemoration near Dungloe, Co Donegal yesterday where he had been the speaker.
A senior member of Sinn Féin, Mr Donaldson was shot dead at a cottage near Glenties in west Donegal in April 2006 months after he admitted that he had been an agent for British intelligence services.
In April 2009, in its Easter message, the Real IRA claimed responsibility for the murder.
Mr Donnelly, was elected as an independent member of Derry City and Strabane District Council in 2014, was arrested as he left the commemoration at Meenbanad in west Donegal. The event was organised to commemorate the centenary of a republican rescue of two local men who were being taken by train by the British army and RIC to face trial in Derry.
Event organiser, Donegal independent councillor, Micheál Cholm Mac Giolla Easpaig, said Mr Donnelly was arrested in connection on foot of a warrant issued on November 22 last year.
Mr Mac Giolla Easpaig, who visited Mr Donnelly at Letterkenny Garda Barrack, said: “I believe it is part of an ongoing campaign of harassment against independent socialist republicans who are arguing against the government in Dublin and in the Six Counties.”