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SYDNEY, June 28 (Reuters) - A magnitude 6.7 earthquake struck the Bougainville region of Papua New Guinea on Thursday, the U.S. Geological Survey said on its Web site (http://earthquake.usgs.gov/).

There were no immediate reports of casualties or damage from the quake, which had an epicentre 10 kilometres (six miles) under the sea bed.

USGS said the epicentre was 220 km (135 miles) south south-west of Arawa on Bougainville island, and about 250 km west of Gizo in the Solomon Islands, where a tsunami killed at least 34 people and destroyed up to 2,500 homes on April 2.

The Hawaii-based Pacific Tsunami Warning Centre's Web site (http://www.prh.noaa.gov/ptwc/) said there was no threat of a destructive or widespread tsunami following the quake, based on historical data.

Papua New Guinea's Geophysical Observatory in Port Moresby said the quake hit at 12:52 p.m. local time (0252 GMT) in an area well known for earthquakes.

"We understand there will not be much disturbance tsunami-wise," the observatory's Mathew Moihoi told Reuters from Port Moresby, adding authorities were still checking for any localised damage from the quake.

Papua New Guinea and the neighbouring Solomon Islands lie on the so-called Pacific "Ring of Fire", where volcanic activity and earthquakes are common. ((Reporting by James Grubel, editing by Jerry Norton; james.grubel@reuters.com; Reuters Messaging: james.grubel.reuters.com@reuters.net, +612 6273 2730))

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