A 22 year old man has been arrested after allegedly making a threat at Christchurch's New Brighton Work and Income office.

The incident happened around 10 30 this morning.

It prompted a shut-down off all Work and Income offices across Canterbury.

Police won't give more information, but senior sergeant Roy Appley says the man threatened to harm people as he left the premises.

"A short time later the police spoke to that male and arrested him and are looking to charge him with an offence in relation to that."