Strong quake near Tonga prompts tsunami warning

A powerful 7.9-magnitude earthquake struck Friday in the Pacific Ocean, shaking an erupting underwater volcano off Tonga's main island and raising fears of increased lava and ash flows, officials said.

There were no immediate reports of injury or damage from the quake, which was felt more than 3,000km away in New Zealand. A tsunami warning for islands within 1,000km of the epicentre was cancelled two hours later.

"We are quite lucky not to get a tsunami," Tongan government chief seismologist Keleti Mafi told The Associated Press.

But he warned the powerful quake "will directly affect the eruption" of the volcano about 10km from the southwest coast of Tongatapu island and could lead to more molten lava and ash flowing into the sea. A column of smoke and steam was rising 20km into the sky.

"The strength of the earthquake could crack the volcano's (undersea) vent and allow more magma (molten rock) to be ejected," Mafi said.

A check of the volcano Thursday from a boat 3.2km away from the vent showed about "a 10-meter (33-foot) depth of lava at the vent" standing up out of the ocean.

"It's grown out of the sea," he said, adding the violent eruption meant "it's very risky to go closer."

With most of the volcano underwater, much of the ash was soaking into the water rather than spewing high into the air.