A 6.5-magnitude earthquake hit off the Solomon Islands on Sunday, the latest powerful aftershock following a 8.0-magnitude quake that sparked a tsunami four days ago, US seismologists said.

The US Geological Survey said the quake struck at 8.02am (2102 GMT on Saturday/0232 IST) 29 kilometres (18 miles) south-southwest of Lata, the main town on remote Ndende island in the Santa Cruz Islands, which are part of the Solomons, at a depth of 18 kilometres.

It was the latest in a series of powerful aftershocks to hit the remote region since a deadly 8.0-magnitude earthquake on Wednesday triggered a tsunami, killing at least 13 people, destroying villages and leaving thousands homeless.

The tremor was not expected to generate a widespread tsunami, the Pacific Tsunami Warning Center said.

Geoscience Australia also measured it at 6.5 but centred at a greater depth of 36 kilometres.

A further 12 houses were reported destroyed following a 6.8 magnitude tremor Friday and another measuring 7.0, which sent villagers fleeing to higher ground in fear of another tsunami.

The Solomon Islands government has declared the outlying Santa Cruz Islands a disaster area as the aftershocks continue to hamper relief efforts.

Because of a fragile communications system, officials in the capital Honiara were struggling to get a clear picture of the extent of damage, but the Red Cross said food, water and shelter were a priority for quake-hit villages.