The Royal New Zealand Airforce has joined a search for an emergency beacon that's been activated in the South Pacific.

Photo: Twitter / NZDF

The distress signal was made close to Niulakita Island, the southernmost island of Tuvalu, 3700 kilometres north of New Zealand.

Air Commodore Andrew Clark said an Orion aircraft took off this afternoon at the request of the Fiji's Rescue Coordination Centre.

"The coordinates from the distress call were used to define the search area and will hopefully help us pinpoint the beacon's location," Mr Clark said in a statement.

"At present, all we know is that a beacon has been activated in the vicinity of Tuvalu and we are helping Fijian authorities locate it."

The Rescue Coordination Centre New Zealand said it had asked all vessels within 500 kilometres of where the beacon was activated to be on the lookout for any signs of distress.