A third powerful aftershock has rattled the Solomon Islands as aid agencies struggle to get a clear picture of the devastation five days after a 8.0-magnitude quake triggered a deadly tsunami.

Two boats carrying urgently needed supplies of medicine, food, water and tents have arrived at Lata, the main town in the island group, but the fragile communications system meant further shipments were on hold.

Officials in the capital Honiara said they had not been able to receive full assessments of the situation in the outlying islands.

"At the moment we don't know if we are still in the relief stage or have moved to the recovery stage," Red Cross secretary general for the Solomon Islands, Joanne Zoleveke, told AFP.

"We don't know if what we have sent is sufficient or if more is required and we have to charter more boats. We can't make those decisions until we receive assessment reports from Lata and communications are intermittent."

A 6.3 magnitude earthquake jolted the region early on Monday and was centred 51km southwest of Lata at a depth of 35km.

It followed a 6.5-magnitude quake early on Sunday which was centred just 29km south-southwest of Lata at a depth of 18km, and a 7.0 aftershock late on Friday night.

The Solomon Islands government has declared the Santa Cruz Islands a disaster area. Aerial surveys indicate most of the damage is confined to the Lata region.

It was estimated about 590 houses had been destroyed, with most of the destruction caused in the initial earthquake on Wednesday and the metre-high tsunami which swept through coastal villages soon after.

Initial reports put the death toll at 13, but Ms Zoleveke said the intermittent communications with Lata indicated it was not that high.

"The official death toll is now 10 as of last night. The body of a child was found in a ditch," she said.

Australia pledged additional aid on Sunday, with Foreign Minister Bob Carr travelling to the Solomon Islands to tour tsunami-wrecked areas. Canberra has already donated $250,000 to the local Red Cross.

Senator Carr announced funding for an emergency flight of three doctors and three nurses to the devastation zone, with the return flight due to ferry severely injured patients back to the capital for treatment.

"We're deploying two AUSAID workers to get into Lata to assess the damage and help co-ordinate relief, and a medical flight to the disaster zone," he said.

"We'll fund the evacuation of two people injured in the tsunami to get hospital treatment elsewhere in the Solomons."

AFP