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.