Office workers wait at an open area outside the building in the business district in Jakarta, after tremors were felt from an earthquake on Indonesia's nearby Sumatra island, 12 Sep 2007

A powerful earthquake has struck off the coast of Indonesia's West Sumatra island, shaking buildings as far away as Singapore and triggering tsunami warnings throughout the region. Scientists measured the quake at a magnitude of 7.9.

Scientists at the U.S. Geological Survey say the epicenter of Wednesday's quake was more than 600 kilometers northwest of the Indonesian capital Jakarta, and at a depth of more than 30 kilometers.

The quake stuck off the southern coast of West Sumatra at about 6:10 p.m. local time (1110 UTC) and toppled at least one building in Bengkulu, a town near the quake's epicenter.

The extent of the damage was unclear, but there were various reports of toppled buildings near the epicenter and in West Sumatra's provincial capital of Padang.

The Pacific Tsunami Warning Center said the quake had the potential of generating a large tsunami wave that could affect coastlines across the Indian Ocean basin.

However, several hours after the quake hit, Indonesia lifted its tsunami warning. Other watches remained for the Andaman and Nicobar islands in the Bay of Bengal and for coastlines in Malaysia and Sri Lanka.

In December 2004, a massive undersea earthquake and tsunami killed more than 160,000 people in Indonesia's westernmost Aceh province. Many thousands more were killed in other Indian Ocean nations.

Indonesia is the world's largest archipelago. It is prone to seismic upheaval because of its location on the so-called Pacific Ring of Fire, an arc of volcanos and fault lines encircling the Pacific Basin.

Some information for this report was provided by AP and Reuters.