UPDATE 12.30pm:

Reports are coming in about a number of armed police being spotted in the Merivale area.

A reporter at the scene says road blocks are in place.

"The road is blocked off near Landview Rd and Merivale Rd.

"There are a number of plain-clothed police officers as well as armed police in the area."

Another witness says it's happening at a property at the back of Merivale School.

"I'm in Gate Pa watching from my house, police are on loud speaker trying to call the person out and dogs are barking.

"Looking from Mansels it's the house to the far right and back-end of the school field.

"There is a police car on Mansels Rd and maybe near the back entrance of the school.

"I don't know whats going on, it sounded like a crash at first, I don't know if police have knocked the door down."