UPDATED 11.37am: Armed police are parked up on a street in Nelson.

Three schools and a kindergarten are in lock-down following an armed offenders squad callout in Nelson this morning.

Nelson Intermediate principal Hugh Gully said they got a call from police, telling them to get their kids inside.

"We have procedures that we follow so we're in full lockdown, but everyone's calm."

NZME's Darryn Palmer said police were called to the area in Nelson south, when they heard reports of a person carrying a gun about an hour ago.

They're focusing on a house in Brunner street, but they've cordoned off a number of other streets.

He described the scene involving "at least six armed offenders squad members, as well as regular police who are also armed on cordons on the Waimea Road and Tukuka Street."

Waimea Road is a main road through Nelson.

NZME's Emma Helleur said she's by Tukuka Street and police are blocking the road, with armed offenders officers and two dog units.

She said police aren't letting people down towards Campbell or Motueka Street.

"From what I can see he's got a bullet proof vest on and he's definitely holding one of the police rifles."