Ash from an underwater volcano north-west of the Tongan capital has forced several airlines to cancel flights in and out of the country.

Air New Zealand said ongoing volcanic activity in Tonga caused the cancellation of some if its services between New Zealand and Tonga.

It said flight NZ970, an Auckland to Nuku’alofa flight on Monday, was diverted to Samoa and later returned to Auckland. Another flight from Nuku’alofa to Auckland was cancelled.

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The airline said regular services were also cancelled on Tuesday, as well as an additional return service meant to re-accommodate Monday’s affected passengers.

Air New Zealand said it had scheduled additional services later in the week, in order to re-accommodate affected customers, but that would be subject to conditions improving.

Virgin Australia said some of its flights to and from Tonga had also been cancelled due to the volcanic ash cloud.

The airline said it would be putting on an additional service from Sydney to Tonga’s Fuaamotu International Airport on Wednesday.

“The forecast for tomorrow is looking a lot better so we’re confident things will return to normal,” a spokeswoman said.

Ash sent more than 9,000 metres into air: meteorologist

New Zealand Civil Aviation Authority meteorologist Peter Lechner told Radio New Zealand the volcano was sending volcanic ash more than 9,000 metres into the air.

A vulcanologist from the Institute of Geological & Nuclear Science in New Zealand, Brad Scott, told Pacific Beat the volcano began erupting about December 20.

He said the last eruption was in 2009, but it also erupted in 1988, 1937 and 1912.

PHOTOS: Massive ash cloud as Tonga volcano erupts http://t.co/Sml5cz6uT7 pic.twitter.com/br2uSla0ZA

— RadioLIVE (@RadioLIVENZ) January 13, 2015

Mr Scott said the volcano started causing some visibility problems for airlines about two days ago.

“The last couple of days the trade winds have sort of backed off and it has become sort of unstable and the wind direction has become unsteady and it’s not changing,” he said.

“In particular, the plumes have been heading towards the main island Nuku’alofa and that has created some issues for aviation, so being risk averse they have been stopping flights while the wind direction has flown towards the airport.”

Residents in Tonga described the eruption as a spectacular sight.

They said the enormous plume from the volcano had shot high into the sky and a muddy discharge underwater turned areas of the sea off the island blood red.

“I feel it is healthily letting off steam, but it is growing,” resident Chris Egan told the Stuff.nz website.

“The base has doubled in size since December 24, when we first saw it again.

“And it’s getting higher. This one will not give up.”

There was no damage reported and New Zealand’s Volcanic Ash Advisory Centre said the ash cloud was expected to dissipate by the end of Tuesday.