Two men being held in connection with the murder of prison officer David Black have been released without charge.

High profile republican Colin Duffy, 44, and a second man, aged 29, were detained in Lurgan, Co Armagh, just miles from where Mr Black was ambushed on the M1 motorway on his way to work at the top security prison, near Lisburn, Co Antrim.

A spokeswoman for the PSNI said the pair had been released unconditionally.

A third man arrested by Gardai is still being questioned in Co Leitrim.

Duffy has been cleared of murder charges on three separate previous occasions - the latest last January after two soldiers were shot dead outside Massereene Army barracks in March 2009.

He was arrested on Friday at his home in the Kilwilkie estate.

Meanwhile, detectives have appealed for information about a Dublin-registered Toyota Camry used by the killers. The dark blue car had a registration plate 94 D 5099.