A man is being questioned in connection with the murder of senior Real IRA member Alan Ryan in Dublin.
The dissident republican was shot dead close to his home in Clongriffin on Monday afternoon.
Armed gardaí have been on patrol since the killing, and have stepped up security ahead of his funeral at the Church of the Holy Trinity in Donaghmede today.
Gardaí in Coolock arrested a man in his 40s last night, but declined to say where he is being questioned.
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A spokesman said he was being detained at a north city Garda station under section 30 of the Offences Against the State Act.
He can be held for up to three days.