A deep 7.0-magnitude earthquake struck near the Northern Mariana Islands in the western Pacific on Tuesday, the US Geological Survey said, but no tsunami warning was issued.

The quake hit 42 kilometres (26 miles) west of Agrihan and 395 kilometres north of the main island Saipan, but it was at a depth of 603 kilometres and seismologists said it was too deep to cause any impact.

"Obviously people may get a small shake but there's hardly any population around there," Geoscience Australia seismologist David Jepson told AFP.

"There's definitely no tsunami and it was too deep and too far away from anywhere to have caused any damage."

A self-governing commonwealth of the United States since 1976, the Northern Marianas consists of 15 islands, with more than 90 percent of the population of 54,000 living on Saipan. Only four other islands are populated.