An official of the U.S. National Park Service said there had been an unknown number of deaths in American Samoa. In nearby Western Samoa, there were also reports of deaths and houses destroyed. In New Zealand, authorities ordered people in low-lying coastal homes and camping grounds to evacuate.
"I can confirm there is damage, I can confirm there are deaths and I can confirm there are casualties," a Western Samoa police spokeswoman said by phone.
"I cannot say any more at the moment."
A resident of a Western Samoan coastal village, Theresa Falele Dussey, told Radio New Zealand her house had been destroyed by wave, as were houses and cars in a nearby village.
"Several people have been calling up the radio stations to report high sea swells hitting the coastal areas of Fagaloa and Siumu on the eastern side of Upolu island and along to the south," said Samoalive News (www.samoalivenews.com )
"School has been called off for the day with tsunami warnings calling for people to head to higher grounds."
The tsunami caused waves of 5.1 feet (1.57 metres) above normal sea level off American Samoa, according to the Pacific Western Tsunami Warning Center in Hawaii, triggering an alert that sent people across the region fleeing for higher ground.
There were unconfirmed reports of even larger waves hitting American Samoa, reaching about 800 metres inland.
Experts said the wave was not expected to be as large as the 2004 Asian tsunami, which killed about 230,000 people in 11 countries, but warned people across the region to either head for higher ground or stay away from the coast.
New Zealand authorities expected a wave of about one metre to hit the country's east coast between 2040 GMT and 2140 GMT.
The Cook Islands and nearby Niue were also on alert but there no immediate reports of damage from either.
The region is home to tens of thousands of islanders living at sea level.
Hawaii Monitors Situation
"The National Park of American Samoa visitor center and its offices appear to be destroyed completely," said Holly Bundock, spokeswoman for the National Park Service's Pacific West Region in Oakland California.
Nathan Becker, an official at Pacific Western Tsunami Warning Center, told MSNBC a tsunami wave can dissipate or grow larger and go all the way across the ocean.
The epicenter of the quake was located 120 miles (190 km) southwest of American Samoa, a remote Pacific island, the U.S. Geological Survey. The USGS earlier said the quake measured 7.9 magnitude. It struck at a depth of 11.2 miles (18 km).
Hawaii was monitoring the situation.
CNN said that if a tsunami hit Hawaii, it would arrive at at about 7:18 EDT (2318 GMT).
Chevron Corp said it was monitoring the tsunami threat to Hawaii, where the company has a 54,000 barrel per day (bpd) refinery near Honolulu.
Tesoro Corp did not immediately reply to messages about its 93,500 bpd refinery at Ewa Beach, also on the Hawaiian island of Oahu.
Both refineries provide jet fuel to commercial airlines and the U.S. military complex at Pearl Harbor as well motor fuels.
