MEDAN, Indonesia -- A major underwater earthquake struck the Sumatran coast late yesterday, killing hundreds of people on a nearby island and spreading fears across the Indian Ocean region that another tsunami was on the way. Indonesia's vice president predicted up to 2,000 deaths.
Tsunami warnings resounded overnight in six Indian Ocean countries, but no catastrophic waves were reported in the region, where a larger quake and tsunami in December killed at least 175,000 people and left more than 100,000 missing.
Coastal residents panicked and raced to higher ground in parts of Indonesia's Sumatra island, although the panic eased within hours in many areas. Sirens and alarms blared in Sri Lanka, India, and Thailand, which also were hit hard in the previous disaster.
Yesterday's earthquake had a magnitude of 8.7, according to the US Geological Survey. Along with the magnitude 9.0 quake on Dec. 26, it ranks among the 10 biggest quakes since 1900. Officials said it was large enough to have produced deadly waves and widespread devastation. People reported feeling the tremor hundreds of miles away in Thailand and Malaysia.
The quake was registered at 11:09 p.m. local time yesterday and lasted for several minutes, according to the USGS. It struck 19 miles under the seabed. The epicenter was 75 miles off the western coast of Sumatra, 120 miles southeast of the earlier temblor.
Yesterday's temblor, although very powerful, had but a fraction of the explosive power of the earlier quake. December's quake was equal to 100 million pounds of TNT; it caused the seabed to spring up as much as 60 feet.
Terrified of a disaster of equal proportions, authorities yesterday issued tsunami alerts for six Indian Ocean countries after the quake struck: Indonesia, Sri Lanka, India, the Maldives, Malaysia, and Thailand.
On Nias island, about 45 miles south of the epicenter and 800 miles northwest of Jakarta, the Indonesian capital, officials described destruction and significant loss of life. Most of the deaths reported in the hours after the quake struck were in Nias, officials said.
''About the victims, we cannot count them now. We only know there are many buildings flattened," said Zulkifly Sirait, a police sergeant, quoted by the Reuters news service.
He said there was ''a big possibility there will be hundreds of people killed" in Gunungsitoli, the island's main town, which has about 30,000 people. Nias, a well-known surfing destination, has a population of 638,000. It was hit hard in the earlier quake, with 340 people reported killed and 10,000 made homeless.
The deputy mayor, Agus Mendrofa, said people had fled the seaside town. ''Gunungsitoli is now like a dead town," he said. ''The situation here is extreme panic."
Police pulled bodies out of the rubble of collapsed houses, and a fire was reportedly raging in one part of town. Hundreds of buildings collapsed or were heavily damaged.
In Jakarta, Vice President Jusuf Kalla said in a radio interview this morning that the death toll on Nias could be between 1,000 and 2,000. A spokesman for the country's disaster center said this morning that about 1,000 people were killed on the island.
In Banda Aceh, the capital of Aceh province on Sumatra, people reported tremors that lasted several minutes and said power was lost for about 10 minutes. At least 106,000 people were killed in Aceh in the December tsunami.
Residents said they had been instructed in recent community briefings to seek higher ground if they felt a large earthquake. ''If things happen, we have to leave," said Iwan, a security guard at a house in downtown Aceh, who uses only one name.
Refugees who still live in tents and temporary housing streamed along darkened Banda Aceh streets clogged with cars and motorbikes and fled to higher ground. Some cried and clutched children in their arms. Others sought shelter in mosques.
Yesterday's quake ''was the biggest I've ever felt," said Helene Barnes, regional manager for Asia and Pacific for Fauna & Flora International, an environmental group. But she said that no houses appeared to have collapsed in her area and that her colleagues in Calang on the western coast of Sumatra had reported no damage.
''Here in Banda Aceh, there have been a lot of people panicking. A lot of people running and walking and driving from the sea. It's not an organized evacuation, but lots of people were moving. I can hear lots more vehicles than normal," she said.
At 1:45 a.m., Indonesian Metro TV broadcast footage of a man with a megaphone shouting in Indonesian on the streets of Banda Aceh. ''The situation has returned to normal," he announced. ''The water is not rising. So you can all go back to your homes."
The energy from yesterday's quake appeared to be directed toward the southwest, said Frank Gonzalez, an oceanographer with the National Oceanographic and Atmospheric Administration in Seattle.
Tsunami-caused waves of 10 to 20 inches hit to the north and south of Perth, Australia, officials said. A 10-inch tsunami was reported at the Cocos Islands, 1,400 miles west of Australia. A 16-inch tsunami was reported in the northern Maldive Islands, according to the Pacific Tsunami Warning Center. No major damage was reported from those waves.
Scientists said that while preliminary indications were that no massive tsunami were produced by yesterday's quake, it is possible that one formed and headed out to sea and away from populated areas.
US State Department deputy spokesman Adam Ereli said US diplomatic missions in Asia and Africa went into ''battle mode" to respond quickly to any contingency. Authorities worldwide had been slow to recognize the magnitude of the Dec. 26 disaster.
Ereli said there had been no reports of Americans killed, injured or missing.
Governments in several countries issued warnings based on the possibility of a tsunami because of the quake's intensity.
Indian officials activated a disaster program early today and issued an advisory for eight coastal states, citing the ''possibility of this earthquake triggering a tsunami." Dhirendra Singh, a Home Ministry official, said precautions were needed for six to eight hours after the quake. The advisories were dropped this morning when no tsunami developed.
While officials in Indian Ocean nations have discussed a satellite-based tsunami warning network, it has not yet been implemented.
''Our biggest preparation is that there are no people on the coast," said Shivraj Patil, India's home minister. ''We are asking people not to panic, but at the same time to be vigilant. Every earthquake does not convert into a tsunami."
Officials said after the December disaster that a tsunami early warning system could have saved many lives. Such a system exists in the Pacific but has not yet been established in the Indian Ocean. Japan and the United States had planned to start providing tsunami warnings to countries around the Indian Ocean this month until the region established its own alert system.
Public address systems in the southern state of Tamil Nadu issued alerts and warned some coastal residents to move inland as a precaution. Sri Lankan officials also held emergency meetings and broadcast warnings. Indian television reported incidents of panic along the Sri Lankan coast, with people fleeing their houses.
Material from the Associated Press was included in this report.