A powerful 6.6-magnitude earthquake struck the eastern Indonesian region of Papua on Friday, US seismologists said, causing panicked people to run screaming out of their homes.

No tsunami warning was issued and there were no reports of casualties or damage after the undersea quake hit at about 1:00 am (1600 GMT), some 30 kilometres from the coastal city of Sorong, in West Papua province.

But an AFP journalist said the quake, which struck at a depth of 24 kilometres (14 miles), was felt strongly in the city for about two minutes, and people woke up and ran outside in a panic.

The quake had caused blackouts and residents were staying outside, too scared to return home, he said. But he added there were no signs of damaged buildings or injured people.

Mochammad Riyadi, a senior official from Indonesia's meteorology, climatology and geophysics agency, said there had not been any reports of damage or casualties so far.

"Although the magnitude is big, we are not expecting a major impact as Sorong city is quite sparsely populated," he told AFP.

The USGS initially put the magnitude at 6.9 but then revised it down.

The Pacific Tsunami Warning Center said there was no threat of a tsunami.

Indonesia sits on the Pacific "Ring of Fire", where tectonic plates collide, causing frequent seismic and volcanic activity.

A huge undersea quake in 2004 triggered a tsunami that engulfed Aceh province on western Sumatra island, killing more than 170,000 people in Indonesia and tens of thousands more in other countries with coasts on the Indian Ocean.