A man in a long black trench coat and carrying what looked like a samurai sword forced a school into lockdown and sent armed police to the University of Waikato in Hamilton this morning.

Sixteen police were sent to the university to scour the grounds after reports of an armed man about 9.30am.

It took 90 minutes to track down the man.

He turned out to be a 25-year-old member of the university's sword fighting club, who was in fact carrying an umbrella that looked like a weapon.

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"The sword is actually an umbrella that, when a button is pushed, activates,'' Senior Sergeant Rupert Friend said.

"The man was quite shocked at the response his activities had generated and most apologetic. We are currently working to identify the supplier of these devices and others which include an imitation shotgun.''

Mr Friend said while such items were not illegal, people need to use a "degree of common sense'' about where and how to use them.

"The member of the public who rang 111 died exactly the right thing and we would far prefer to deploy to an incident and find there is no threat than people think they are wasting police time and not call us and we fail to learn of a genuine incident.''

Mr Friend said police worked with the university to send out an alert email to everyone on campus to locate the trench coat-wearing man.

"We're very grateful for that person who saw something that didn't appear right and called 111.

"As in the case with all situations police treated the report seriously and responded accordingly, deploying armed staff to the area while also requiring a local primary school to activate their emergency plan and go into lock down.''