MANILA - A strong earthquake of 6.9 magnitude struck off the southern Philippine island of Mindanao on Saturday, raising fears of dangerous tsunami waves across the region but after about two hours, the tsunami warning was withdrawn.

There were no reports of casualties or damage from the earthquake, which the U.S. Geological Survey (USGS) said struck 193 km (120 miles) east of the Philippine city of General Santos, at a depth of 60 km (37 miles).

The Pacific Tsunami Warning Center initially said "hazardous tsunami waves" were possible within 300 km (186 miles) of the epicentre", along the coasts of the Philippines, Indonesia and the Pacific island nation of Palau.

But about two hours after the quake struck, the center said there was no longer a tsunami threat.

The USGS initially said the magnitude of the quake was 7.2 but later downgraded it to 6.9.

Residents of the southern Philippines said the earthquake lasted about a minute and people rushed out of buildings but there had been no major damage.

"I was at the front desk and saw the chandeliers swaying," Jonna Ramos, who works at the Anchor Hotel in General Santos, told Reuters by telephone, adding that all guests and staff had left the building but later went back in.

Indonesian media also said there were no reports of damage.

The Philippines and Indonesia are both on the Pacific "Ring of Fire", a horse-shoe shaped band of volcanoes and fault lines circling the edges of the Pacific Ocean.

Indonesia has been struck by two serious tsunami this year.

The first followed a 7.5 magnitude quake on the west coast of Sulawesi island in September. More than 2,000 people were killed.

The second tsunami struck a week ago, on Saturday evening, when part of a volcanic island collapsed in the Sunda Strait, between Java and Sumatra islands, generating tsunami waves that killed more than 400 people.

(Writing by Robert Birsel; Editing by Richard Borsuk) ((Robert.Birsel@thomsonreuters.com;))