Two strong 6.8-magnitude earthquakes struck off the Solomon Islands early Saturday, US geologists said, but there were no initial reports of damage and no tsunami warnings were issued.

The first quake hit at a depth of 10 kilometres (six miles), 205 kilometres from Kirakira and 448 kilometres from the capital Honiara and the second shallow quake struck just over two hours later about 159 kilometres from Kirakira.

The Solomons have been rocked by several quakes of 6.0-magnitude or higher in recent days, with the most recent a 6.0 magnitude quake which hit the islands early Friday, and a 6.9 magnitude tremor the day before. No major damage was caused by the earlier tremors.

The Hawaii-based Pacific Tsunami Warning Center said there was no threat of a Pacific-wide tsunami from the Saturday tremors.

Geoscience Australia initially estimated the two latest quakes at the magnitudes of 7.1 and 6.9 but said they were unlikely to cause local tsunamis in the quake-prone region, in part due to their location.

Seismologist Mark Leonerd said it was slightly unusual to have two big quakes "right next to each other" but that seismic activity was common in the region.

The quakes have been followed by fairly typical aftershocks, he said, adding there had also been recent activity in nearby Papua New Guinea.

"That sort of area is putting on a little bit of activity at the moment," he said.

The Solomons are part of the Pacific "Ring of Fire", a zone of tectonic activity known for its frequent earthquakes and volcanic eruptions.

In 2013, the Solomons were hit by a tsunami after an 8.0-magnitude quake, leaving at least 10 people dead and thousands homeless after buildings were destroyed.