A car is seen pushed up against a bridge after a surge of sea water from a tsunami filled a small stream in the village of Fagatogo in American Samoa on Tuesday. (Fili Sagapolutele/Associated Press)

Tsunami waves spawned by a powerful earthquake swept ashore on two South Pacific island chains early Tuesday, killing dozens of people and leaving others missing at devastated National Park Service facilities.

A total of 63 people were confirmed dead on Samoa and 19 more on American Samoa, but officials acknowledged that with many missing, the death toll seemed certain to rise.

"I don't think anybody is going to be spared in this disaster," said acting American Samoa Gov. Faoa A. Sunia.

Sunia declared a state of emergency in American Samoa, describing "immense and widespread damage to individual, public and commercial buildings in coastal areas" along with death and injury.

Gov. Togiola Tulafono, who was in Honolulu for a conference, told reporters that more victims could be found when rescuers reach areas that are inaccessible by roads. Tulafono said a member of his extended family was among the dead.

New Zealand's acting Prime Minister Bill English said any death tolls for the Samoas were only "guesses" so far, and that there were unconfirmed reports of five additional people dead in the island nation of Tonga, west of the Samoas.

"There are a considerable number of people who've been swept out to sea and are unaccounted for," English said. "We don't have information about the full impact and we do have some real concern that over the next 12 hours the picture could look worse rather than better."

Christopher Moore looks at a computer image of the tsunami at the Pacific Tsunami Warning Center in Ewa Beach, Hawaii, on Tuesday. (Hugh Gentry/Reuters)

The quake, with a magnitude between 8.0 and 8.3, struck around dawn about midway between Samoa and American Samoa.

Holly Bundock, spokeswoman for the National Park Service's Pacific West Region in Oakland, Calif., spoke with Mike Reynolds, superintendent of the National Park of American Samoa. From his vantage point under a coconut tree uphill from Pago Pago Harbor; Reynolds reported that the park's visitor centre and offices appeared to have been destroyed.

Bundock said Reynolds and another park service staffer had been able to locate only 20 per cent of the park's 40 to 50 employees and volunteers. The National Park of American Samoa is the only national park south of the equator, a scenic expanse of reefs, picturesque beaches, tropical forests and wildlife that include flying foxes and sea turtles.

In Washington, U.S. President Barack Obama issued a disaster declaration, making federal funds available to victims in American Samoa.

The Federal Emergency Management Agency said it was deploying teams to American Samoa to provide support and assess damage.

A map shows the location of an earthquake having a preliminary magnitude of 8.3 occurring in the Samoa Islands region of the Pacific Ocean. New Zealand can be seen at the centre and Australia at left. (NOAA/NWS/West Coast and Alaska Tsunami Warning Center/Handout/Reuters)

Residents in both Samoa and American Samoa reported being shaken awake by the quake, which lasted two to three minutes and was centered about 32 kilometres below the ocean floor. It was followed by at least three large aftershocks of at least 5.6 magnitude.

The ramifications of the tsunami could be felt thousands of kilometres away, with federal officials saying strong currents and dangerous waves were forecast from California to Washington state.

No major flooding was expected, however.

The earthquake and tsunami were big, but not on the same scale of the 2004 Indonesian tsunami that killed more than 150,000 across Asia the day after Christmas in 2004, said tsunami expert Brian Atwater of the U.S. Geological Survey in Seattle.

The 2004 earthquake was at least 10 times stronger than the 8.0 to 8.3 measurements being reported for Tuesday's quake.