A 5.7 magnitude earthquake struck off Vanuatu early this morning but no tsunami warning was immediately issued.

The US Geological Survey says the quake hit just after 1 o'clock, 157 kilometres south-east of the capital city of Port Vila.

It was registered at a depth of 38 kilometres.

It was the second earthquake to strike the area in three hours, following a 5.1 magnitude quake earlier.