Armed police swooped on a man in Lincoln Road after a reported public order incident involving a weapon.
The Triangle was closed this afternoon (Saturday) by officers who were called out at 4.20pm.
A man in his 20s was arrested with police saying an imitation firearm has been discovered at the scene which is believed to be linked to the offence.
No armed police remain at the scene with police not looking for anybody else in relation to the incident.
Buses have been diverted due to the police incident.