A member of the Australian Navy, left, helps a Solomon Islands' police officer today load relief supplies for the tsunami-hit region of Gizo onto a ship in Honiara, Solomon Islands. A powerful magnitude-8 earthquake struck off the Solomon Islands, creating a tsunami in the islands' Western Province today. Arthur Wate | AP Photo/Solomon Star

A wall of water reportedly 30 feet high struck the island of Choiseul and swept a third of a mile inland, while smaller but still destructive waves surged ashore elsewhere in the western part of the impoverished archipelago, causing widespread damage and leaving thousands homeless.

The tsunami was triggered by a magnitude-8.0 quake that struck shortly after 7:39 a.m. today (10:39 a.m. Hawai'i time yesterday) six miles beneath the sea floor, about 25 miles from the western island of Gizo and 215 miles northwest of the Solomons' capital, Honiara, the U.S. Geological Survey said.

The quake — the strongest in the Solomons in more than three decades — set off tsunami alarms from Tokyo to Hawai'i and closed beaches along the east coast of Australia more than 1,250 miles away. Lifeguards with bullhorns yelled at surfers to get out of the water at Sydney's famous Bondi Beach.

The danger passed quickly, but officials rejected suggestions they overreacted, adding that the emergency tested procedures put in place after the 2004 Indian Ocean disaster that left 230,000 dead or missing in a dozen countries.

Up to 4,000 people were camped on a hill behind Gizo (pronounced GEE-zoh), a town of about 7,000, said Alex Lokopio, premier of hard-hit Western Province. Floodwaters subsided, but the Red Cross reported about 500 houses were damaged or destroyed, leaving 2,000 homeless. Many people were too scared to return to the coast amid more than two dozen aftershocks, including at least four of magnitude-6 or stronger.

Initial reports from other islands suggest similar or worse levels of damage, the Red Cross said. Roads were inaccessible and there was heavy damage to infrastructure, including phones and electricity, said Martin Blackgrove, the International Red Cross' regional disaster management coordinator for the Pacific, based in Fiji.

Because of Gizo's proximity to the quake's epicenter, the tsunami struck before an alarm could be sounded.

"There wasn't any warning — the warning was the earth tremors," Lokopio told New Zealand's National Radio. "It shook us very, very strongly and we were frightened, and all of a sudden the sea was rising up."

Within five minutes, a wall of water up to 16 feet high plowed into the coast, inundating homes, businesses, a hospital, schools and two police stations, and dumping boats into streets in Gizo, a popular spot for diving, witnesses and officials said.

Outlying villages, where many houses are flimsy wooden structures, may have fared worse, based on scattered reports from residents with two-way radios.

"It was just a noise like an underground explosion," Gizo resident Dorothy Parkinson told Australia's Nine Network television. "The wave came almost instantaneously. Everything that was standing is flattened."

Judith Kennedy said water "right up to your head" swept through town. Her father, dive shop owner Danny Kennedy, said Gizo was devastated when the wave subsided.

"There are boats in the middle of the road, buildings have completely collapsed and fallen down," he told The Associated Press.

Alfred Maesulia, a spokesman for Prime Minister Manasseh Sogavare, told the Sydney Morning Herald that some coastal villages were struck by waves up to 30 feet tall, although most reported heights of between 9 and 15 feet.

"There are reports that some villages were completely washed away," he told AP.

Maesulia said the death toll was expected to rise as the cleanup progressed.

"Some people were seen floating on the sea during the big waves but it was very difficult to go near them," he told the AP. "The number at the moment is 13. It's possible that number will increase, maybe double up or even more."

Villagers on Simbo, Choiseul and Ranunga islands reported deaths and widespread destruction, he said.

"Sasamungga village is quite a big village. ... It was reported that 300 houses were completely destroyed in that village alone."

Sogavare declared a national state of emergency and held meetings with his impoverished country's aid donors about getting help. "My heart goes out to all of you at this very trying time," he said in an address to the nation.

Debris needed to be cleared before Gizo's airfield could be fully operational, the Red Cross said.

Fresh water was in short supply in some areas, while temporary, localized food shortages have also been reported, it said. Some of the affected areas can only be reached by boat.

A damage assessment team flew over the tsunami zone late today, then reported back to the government in Honiara, National Disaster Management Office spokesman Julian Makaa said.

Helicopters made the first drops of tents, drinking water and other supplies to the crowd on the hill behind Gizo, said Peter Marshall, the Solomons' deputy police commissioner. Flights were expected to resume Tuesday.

One boat carrying relief supplies left Honiara for Gizo, and at least three more were expected to go Tuesday, Makaa told the British Broadcasting Corp.

The Australian government pledged $1.6 million in emergency aid and said helicopters already in the Solomons as part of a multinational security mission had been made available for rescue and relief.

The International Federation of Red Cross and Red Crescent Societies said it was releasing $53,000 in initial aid to the national Red Cross.

The archipelago has more than 200 islands with a population of about 552,000 and lies on the Pacific Basin's so-called "Ring of Fire," an arc of volcanos and fault lines where quakes are frequent.

The Hawai'i-based Pacific Tsunami Warning Center initially issued warning bulletins for the Solomons and neighboring Papua New Guinea, and lower-level alerts for most other South Pacific countries, eastern Australia and Hawai'i.

The warnings outside the Solomons' zone were lifted within hours, but Australian officials closed beaches, stopped ferry services in Sydney, closed some schools and warned fishing boats to return to port.

"We just feel it's best to err on the side of caution," said Warren Young, the chief lifeguard on the Gold Coast, about 1,370 miles from the quake's epicenter.

All canceled services in Australia resumed by late today.

The quake occurred when the Australian tectonic plate suddenly dived beneath the Pacific plate, said David Wald of the USGS National Earthquake Information Center in Colorado.

The undersea temblor lifted the ocean bottom, generating deadly tsunami waves near the epicenter, Wald said. A quake of that magnitude rarely causes tsunami damage far away, he said.

"It would have been a much worse situation if the cities were heavily populated," Wald said.

The Solomon Islands has been rocked by several strong earthquakes in recent history.

In 1971, the region was hit by temblors of magnitudes 8 and 8.1. In 1939, two more quakes of magnitudes 7.7 and 7.9 hit the islands, according to the USGS.

The Solomon Islands experienced the last strong quake in 2003 when a magnitude-7.3 struck the region.