Police have arrested a man and seized a crossbow after reports that the man had been threatening residents of a Darwin housing complex.

Police arrested the man about 12.50pm (CST) on Thursday, following reports from the man's relative that he was armed and threatening residents in the Johns Square housing complex in Progress Drive, Nightcliff.

They later confiscated a crossbow from a unit in the complex.

Fourteen armed police officers cordoned off parts of the street and a nearby childcare centre.

Senior Sergeant Bob Harrison said the man gave himself up after speaking to police.

"The person just made threats and we had to take it seriously," he told reporters in Nightcliff.

"The gentleman actually exited the unit himself, he actually didn't know what was happening and he ... came to us voluntarily."

The man was known to police and is expected to be reviewed under the Mental Health Act.

Police are expected to lay charges but not oppose bail, Sen Sgt Harrison said.