SYDNEY, Jan. 22 (Xinhua) -- The Pacific Tsunami Warning Center in Hawaii has issued an alert for the Pacific after a powerful 7.9-magnitude earthquake struck Papua New Guinea on Sunday.

The undersea earthquake struck 41 km northwest of Panguna on the Papua New Guinea autonomous island of Bougainville at 15:30 local time (0430 GMT), the U.S. Geological Survey (USGS) said.

The USGS initially put magnitude of the massive earthquake at 8.0, and then downgraded it to 7.9 magnitude.

"Hazardous tsunami waves from this earthquake are possible within the next three hours along some coasts of Papua New Guinea, the Solomon Islands, Nauru, Pohnpei, Kosrae, Vanuatu, Chuuk and Indonesia," Pacific Tsunami Warning Center said in a statement.

"Tsunami waves reaching 0.3 to 1 meter above the tide level are possible for some coasts of Solomon Islands and Papua New Guinea," the statement said.

There is no tsunami threat to the Australian mainland, the Joint Australian Tsunami Warning Centre said.