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"Hazardous tsunami waves from this earthquake are possible within the next three hours along some coasts of Solomon Islands, Vanuatu, Papua New Guinea, Nauru, New Caledonia, Tuvalu and Kosrae," the US-based Pacific Tsunami Warning Centre (PTWC) said earlier.

The PTWC said the tsunami threat had now largely passed, but that local government agencies would continue to monitor any potential threat.

The monitoring body had said tsunami waves of between one and three metres above the tide level were possible along some coasts of Solomon Islands, while waves of between 0.3 and one metre were forecast for some coasts of Papua New Guinea.

The quake struck at 4:38am AEDT at a depth of roughly 48 kilometres, USGS said — it was initially reported to be of magnitude-8.0.

Loti Yates from the National Disaster Management Office in the capital Honiara said there had been reports of houses collapsing due to the quake.

"There could be possible tsunamis on the south-west of Makira and Temotu, so we are issuing tsunami alerts for those two provinces."

Mr Yates said poor communication infrastructure had made it hard to assess the immediate impact in Makira.

"[One community] that has been in touch with us said they are calling from up the hills, which is good, they activated their own emergency plans and know what to do, so we are happy.

"The warning has been issued ... at this stage, communication difficulties are hampering our ability to get clear information."

Australian authorities said there was no risk to its coastlines, while the New Zealand Civil Defence office said it was evaluating the threat.

The PTWC will issue messages hourly until the threat has passed, it said.

ABC News