PADANG, Indonesia, Sept 30 (Reuters) - A major earthquake of magnitude 7.6 struck off the city of Padang on the coast of Indonesia's Sumatra island on Wednesday, damaging houses, bringing down bridges and starting fires, a witness said.
It was unclear if there were any casualties.
The quake was felt around the region, with some high-rise buildings in the city state of Singapore, 275 miles (440 km) to the northeast, evacuating their staff.
A regional tsunami warning was issued, the Pacific Tsunami Warning Centre. Japan said no tsunami was expected there.
"Hundreds of houses have been damaged along the road. There are some fires, bridges are cut and there is extreme panic here maybe because water pipes are broken and there is flooding in the streets," said a Reuters witness in the city.
Phone lines were down.
Padang, the capital of Indonesia's West Sumatra province, sits on one of the world's most active fault lines along the "Ring of Fire" where the Indo-Australia plate grinds against the Eurasia plate to create regular tremors and sometimes quakes.
A 9.15 magnitude quake, with its epicentre roughly 600 km (373 miles) northwest of Padang, caused the 2004 tsunami which killed 232,000 people in Indonesia's Aceh province, Thailand, Sri Lanka, India, and other countries across the Indian Ocean.
The depth of Wednesday's earthquake was measured at 85 km (53 miles), the United States Geological Survey said. It revised down the magnitude of the quake from 7.9 to 7.6.
A series of tsunamis earlier on Wednesday smashed into the Pacific island nations of American and Western Samoa killing possibly more than 100 people, some washed out to sea, destroying villages and injuring hundreds.
Geologists have long said Padang, with a population of 900,000, may one day be destroyed by a huge earthquake because of its location.
"Padang sits right in front of the area with the greatest potential for an 8.9 magnitude earthquake," said Danny Hilman Natawidjaja, a geologist at the Indonesian Science Institute, in February.
"The entire city could drown" in a tsunami triggered by such a quake, he warned.
Several earthquake-prone parts of the country hold tsunami practice drills, and the national disaster service sends alerts via telephone text messages to subscribers.
But some experts have long said Indonesia needs to do more to reduce the risk of catastrophe.
Padang needed to invest in better infrastructure, including more roads and other escape routes, said Hugh Goyder, a consultant for the United Nations' International Strategy for Disaster Reduction, earlier in the year.
"The road goes parallel to the coast, which means it's difficult in some areas to get away from the coast," Goyder said, adding that in one part of the city, the only escape route is a narrow bridge. (Reporting by Telly Nathalia, Writing by Nick Macfie, Editing by Sanjeev Miglani))