SYDNEY -- A strong earthquake hit off the coast of the South Pacific island of Vanuatu on Monday, but Australian seismologists said it was unlikely to have triggered a tsunami or caused other damage.

Geoscience Australia said the magnitude 6.6 undersea quake was centered about 200 kilometers (124 miles) south of Port Vila between Vanuatu and New Caledonia and hit at about 2:03 p.m. (0303 GMT).

"It would have been felt in some of the southern Vanuatu islands," duty seismologist Hugh Glanville told Agence France-Presse, but added that the radius of the quake zone meant it was unlikely to have caused any damage on land.

"We issued a nil threat for Australia in terms of a tsunami warning. There's quite a slim chance there would be a local tsunami -- but it's very unlikely," Glanville said.

Noting that the United States Geological Survey put the quake at magnitude 6.5, Glanville said it was possible that Geoscience Australia could downgrade its magnitude on later data.