The quake struck Thursday 183 miles (294 kilometers) northwest of the Vanuatu island of Santo, and 354 miles (596 kilometers) northwest of the capital of Port Vila, at a depth of 21 miles (35 kilometers).
The Pacific Tsunami Warning Center immediately issued a regional tsunami warning.
There were no immediate reports of injury or damage from officials in Vanuatu, a collection of nearly 200 islands.
The latest warning comes just two weeks after a quake of magnitude 8.3 rocked the South Pacific near Samoa, sparking tsunami waves that killed at least 178 people and devastated coastal villages in Samoa, American Samoa and in northern Tonga.
Meanwhile, the U.S. Geological Survey reported a strong earthquake struck south of the Philippines on Thursday morning local time.
The quake had a preliminary magnitude of 6.7 and was located in the Celebes Sea, 175 miles (282 kilometers) southeast of Jolo, Sulu Archipelago, and 730 miles (1,175 kilometers) south of Manila. The quake hit at 5:41 a.m. Thursday local time.
USGS did not report any damages or injuries.