The building was evacuated and Stone was arrested after he walked into the Stormont parliament building with a bag and left it on the floor, the BBC reported Friday. Police said there were reports of an unspecified device inside the bag.
Stone, a former Ulster Freedom Fighter prisoner who supports British rule in Northern Ireland, reportedly shouted "no surrender" and was seen carrying a firearm, but it was not known Friday whether the weapon was real or a toy, Sky News reported.
"It seems that Michael Stone has gone on the rampage again, in a very dangerous way. But he was stopped," Irish Taoiseach Bertie Ahern said.
"It just shows you exactly what we are trying to get away from in Northern Ireland."
Ohio bar shooting arrested, charged with murder
McPhee, Cokas 'working on their marriage' after affair