At least 28 people were killed, including a New Zealand man, and about 5400 survivors had been left homeless, the Office of Emergency Management said.

Dozens more are missing or injured.

About 1200 Australians live and work in the Solomon Islands -- many in Gizo, the worst-affected area. But the Department of Foreign Affairs does not hold fears for those yet to make contact.

"There are people we haven't been able to reach, but that's because communications are so bad, not because we think there might be something wrong," a spokesman said.

With at least 13 villages wiped out, and no way yet to check on the many small islands in the devastated Western and Choiseul provinces, officials have told the nation to brace for a climbing toll.

As the first slow trickle of aid began to arrive, Western Province Premier Alex Lokopio said 4000 people were huddled in the hills overlooking Gizo, which was hit by a 5m wall of water.

They spent their second night sleeping in the open on high ground, too terrified by a series of fresh quakes to return home.

"My people are sitting down along the road on the hill of Gizo. I can see their eyes crying and they look sad," he said.

"They are facing starvation, no water and no food and shelter."

The US Geological Survey recorded at least 10 strong aftershocks -- measuring between 5.0 and 6.2 magnitude -- following the 8.0 tremor that sparked the tsunami.

Police spokesman Mick Spinks said 13 coastal villages had been destroyed.

Solomons Prime Minister Manasseh Sogavare warned people to expect the death toll to climb.

"We will be needing a mobile hospital facility and I think Australia and New Zealand have kindly offered to come forward on that," Mr Sogavare said.

Aid workers warned of a humanitarian crisis: food, water and medicine are in short supply.

Australia's Council for International Development said aid teams' reports were alarming.

"It's quite devastating, and things are looking bad. You started with poor infrastructure already, and people there are very dependent on aid," Pacific co-ordinator Neva Wendt said.

Caritas spokeswoman Liz Stone said: "This is the tropics. We are concerned about our supply of antibiotics for some of the injuries and anti-malarials for people who are staying outside."

The Regional Assistance Mission to the Solomon Islands – an Australian-dominated UN force to bring political stability to the islands – has been surveying the devastation by helicopter.

RAMSI officers are taking satellite phones to areas where communications have been cut so people can call loved ones.

RAMSI medical teams are also on stand-by.

Dive shop owner Danny Kennedy said about 150 people were trying to clear debris off roads and runways so military aid flights could bring in tents, medicine and food.

"It's basically just houses stacked on top of one another," Mr Kennedy said.

"One village on Simbo was completely wiped out. The entire village is gone, and where the people are we have no idea."

Also on Simbo, a United Church bishop and three of about 100 worshippers were killed when the massive wave swept in during a church ordination.

Mr Kennedy said villagers were too traumatised to search for loved ones under the rubble.