Key Points:

An army truck on a training exercise in Canterbury became stuck in the Waimakariri River, forcing the occupants to swim for their lives, the army has confirmed.

New Zealand Defence Force Captain Paul Milner told NZPA the light army vehicle had sunk during a training exercise this afternoon in Canterbury.

The Pinzgauer truck was a general purpose vehicle and specialist crew and equipment were now being called in to try to retrieve it, he said.

Cpt Milner could not confirm how many people were on board but it was understood up to three army personnel were in the vehicle when it became stuck.

There were no reports of injuries and the personnel were now believed to be on there way back to Burnham military base, he said.

"Our first concern is for the personnel and everyone got out safely," he said.

An investigation into the incident would be carried out, he said.