International aid is now slowly reaching survivors of the tsunami in the Solomon Islands, but damaged airports and continuous aftershocks have hampered the flow of badly-needed food, water and medicine.

Rescue teams have still not reached some outlying villages due to the transport bottleneck.

Adding to the transport woes, many canoes and other boats usually needed to navigate remote canals have sunk and tsunami seawater has contaminated fuel, Western Province Premier Alex Lokopio said.

It is estimated that 15,000 people have lost their homes.

At least 28 people were killed when a magnitude-8.1 earthquake sent giant waves crashing into remote parts of the South Pacific archipelago on Monday. There is still no official count of the number of people who are missing.

However, the number of casualties is expected to rise as neighbouring islands restore their communications links.

On Wednesday, a second magnitude-6.0 earthquake sent fears across the islands that another onslaught of waves could build, but the islanders were spared.

Meanwhile, relief workers say they're seeing the first signs of disease, and drinking water is becoming an urgent need. Some children camped out in hillside shelters unreachable by waves have diarrhea, the Red Cross said.

The relief agency said it has handed out all the emergency supplies it had stored in Gizo, the main town in the disaster zone, and was waiting for new supplies from a New Zealand military transport plane that landed late Tuesday in the nearby island of Munda.

The New Zealand aircraft is to deliver water as well as 1,000 tents and tarpaulins to Munda.

Australia and the U.S. have offered to help as well, but that aid may still be a few days away.

Deputy police commissioner Peter Marshall said that given the destruction, there have been "surprisingly low" mass body counts. And although aerial surveys have spotted floating bodies, "there have been no sightings of large numbers of people who have perished," he said.

Doctors and nurses are to be flown by aircraft on Thursday to treat survivors.

With files from the Associated Press