(CBS/AP) BANDA ACEH, Indonesia - Indonesian authorities said they believed that a tsunami would hit their shores after a massive earthquake struck waters off the country Wednesday, triggering widespread panic as residents along coastlines fled to high ground in cars and on the backs of motorcycles.
The Meteorology, Climatology and Geophysics Body made its announcement, without estimating when the tsunami would come, as a tsunami watch was issued for countries across the Indian Ocean. The government issued another tsunami warning after what an official described as an 8.1-magnitude aftershock rattled Aceh province.
CBS News correspondent Celia Hatton reports from Beijing that downed phone lines and power outages have made it very difficult for the Indonesian government to get information on possible casualties from the earthquake.
Some were screamed "God is great" as they poured from their homes. Others, separated from relatives, cried as they ran frantically through the streets. In Banda Aceh, Aceh's main provincial city, Indonesia's disaster mitigation agency said the power was out as sirens and Koran recitals were heard from mosques around the city.
The U.S. Geological Survey said the 8.6-magnitude quake was centered 20 miles beneath the ocean floor around 269 miles from Aceh's provincial capital.
The tremor was felt in Singapore, Thailand, Bangladesh, Malaysia and India. High-rise apartments and offices on Malaysia's west coast shook for at least a minute.
The Pacific Tsunami Warning Center in Hawaii said a tsunami watch was in effect for Indonesia, India, Sri Lanka, Australia, Burma, also known as Myanmar, Thailand, the Maldives and other Indian Ocean islands, Malaysia, Pakistan, Somalia, Oman, Iran, Bangladesh, Kenya, South Africa and Singapore.
A tsunami watch means there is the potential for a tsunami, not that one is imminent.
Said, an official at Indonesia's Meteorology and Geophysics Agency who goes by only one name, said a tsunami warning has been issued for cities all along the coast of Sumatra island.
President Susilo Bambang Yudhoyono told reporters: "There is no tsunami reported so far, but we remain vigilant."
"Our warning system is working well, and I have ordered the national relief team to fly immediately to Aceh to ensure the situation is under control and to take any necessary action," he said.
"Thanks God, from what I heard there is neither casualties reported nor major damage in Banda Aceh or other places," he added.
There was chaos in the streets, with fierce shaking continuing for nearly four minutes.
Patients in several cities poured out of hospitals, some with drips still attached to their arms. In some places, electricity was briefly cut.
"It wasn't the strongest quake I've felt," said 22-year-old Tuti Rahmi, while trying to reach her brother by phone.
"But it seemed to last forever," she said. "Hopefully there won't be too much damage."
One hour after the temblor, people were still standing outside their homes and offices, afraid to go back inside.
There were several strong aftershocks.
"I was in the shower on the fifth floor of my hotel," Timbang Pangaribuan told El Shinta radio from the city of Medan. "We all ran out. ... We're all standing outside now."
He said one guest was injured when he jumped from the window of his room.
Thailand's National Disaster Warning Center issued an evacuation order to residents in six provinces along the country's west coast, including the popular tourist destinations of Phuket, Krabi and Phang-Nga.
India's Tsunami Warning Center issued a tsunami warning for parts of the eastern Andaman and Nicobar islands, said Kishore Swarna Angel, a scientist at the center.
In Tamil Nadu in southern India, police cordoned off the beach and used loudspeakers to warn people to leave the area.
Satheesh Shenoi, director of the Indian National Center for Ocean information Services, said the chance of a tsunami was diminishing.
"There are no indications of tsunami wave; the instruments are not showing any sea level change," he said.
The quake was felt in Dhaka, Bangladesh, where many people in the city's commercial Motijheel district left their offices and homes in panic and ran into the streets. No damage or causalities were reported.
In Male, the capital of the Maldives, buildings were evacuated.
Indonesia straddles a series of fault lines that makes the vast island nation prone to volcanic and seismic activity.
A giant 9.1-magnitude quake off the country on Dec. 26, 2004, triggered a tsunami in the Indian Ocean that killed 230,000 people, nearly three quarter of them in Aceh.
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