REPUBLIKA.CO.ID, SYDNEY -- An underwater volcano off Tonga was spewing ash high into the air on Tuesday, causing several carriers to suspend air travel to the South Pacific island nation and turning the surrounding ocean blood red, residents and officials said.

The Hunga Tonga-Hunga Ha'apai underwater volcano, located about 65 km (40 miles) north of the capital Nukualofa, was sending volcanic ash up to 4,500 metres (14,765 feet) into the air, the Wellington Volcanic Ash Advisory Centre (VAAC) said.

The volcano, which first erupted in 2009, had been rumbling in recent weeks before exploding violently in the past few days, The New Zealand Herald newspaper reported.

An Air New Zealand flight between Auckland and Nukualofa on Monday was diverted to Samoa and later returned to New Zealand because of the volcano, the airline said in a statement.

A return service had been scheduled to fly on Tuesday, the airline said, but had been cancelled because of volcanic activity. The volcano was not disrupting flights to other regions, it said.

Regional carrier Fiji Airlines also turned around a flight to Tonga on Monday, citing safety concerns, and domestic flights were grounded in Tonga.

Residents in Tonga described a spectacular sight, with the enormous plume from the volcano shooting high into the sky and a muddy discharge underwater turning areas of the sea off the island blood red.

"I feel it is healthily letting off steam but it is growing... the base has doubled in size since December 24 when we first saw it again. And it's getting higher," resident Chris Egan told the Stuff.nz website.

"This one will not give up."

There was no damage reported and New Zealand's VAAC said the ash cloud was expected to dissipate by the end of Tuesday.

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