The Armed Offenders Squad (AOS) was called to assist in executing a warrant in central Whanganui.
Niblett St was closed off at the intersections of Plymouth St and Dublin St on Thursday afternoon.
A Police spokesperson said the squad was called in on a pre-planned warrant but could not provide further information.
The New Zealand Police website says the AOS are sometimes used for pre-planned operations where there was a high risk to officers.
