A huge undersea earthquake struck off Gorontalo coast Sunday, with a meteorology and geophysics official warning of the possibility of a tsunami hitting Sulawesi.

The head of the agency's earthquake center, Fauzi, said the 6.6-magnitude quake was centered at a depth of 62 kilometers under the sea, 90 km southeast of the city of Gorontalo.

There were no reports of casualties or damage, according to the meteorology office.

"We have informed local officials to warn people in the areas that the earthquake is likely to cause a tsunami in the area," Fauzi was quoted by Reuters as saying.

"A tsunami hasn't taken place but people have been evacuated to higher ground."

Sunday's earthquake comes less than a week after another powerful undersea earthquake triggered a tsunami on the south coast of Java island, killing more than 600 people.

Gorontalo Governor Fadel Muhammad told El Shinta radio he had ordered an evacuation of coastal areas after the strong earthquake rattled the northern half of the island at 3:22 p.m.

A Gorontalo resident, Ferry Majoa, told The Jakarta Post by phone that the earthquake struck twice, at 4:22 p.m. and 4:45 p.m.

"The quake has made residents, especially in Bone Bolango area, panic and start to move to higher ground."

He said many residents had left town two days ago, when they learned their areas were listed among high-risk tsunami areas.

"Hopefully, the tsunami warning won't amount to anything," Ferry said.

Indonesia, which sits on the "Pacific Ring of Fire", where continental plates meet causing frequent seismic and volcanic activity, was the nation worst hit by the December 2004 Asian tsunami.