A 7.8 earthquake shook Indonesia's northwest island of Sumatra early Wednesday, prompting a tsunami warning and sending residents rushing for higher ground. There were no immediate reports of widespread damage.
The quake struck at 5:15 a.m. (2215 GMT) and was centered 125 miles (205 kilometers) northwest of Sibolga in Sumatra at a depth of 28.6 miles (46 kilometers), the U.S. Geological Survey said.
The Indonesia Meteorology and Geophysics Agency issued a tsunami warning following the quake, which struck as people in the region were preparing for morning prayers.
"We issued a tsunami warning and are still monitoring situation there," said Fauzi, an official at the agency's Jakarta office.
Fauzi, who uses a single name, said there were no immediate reports of damage or casualties.
The Pacific Tsunami Warning Center in Honolulu also issued a tsunami watch. The center said no tsunami threat existed for other coastal areas in the Indian Ocean, although some areas could experience small sea level changes and strong or unusual coastal currents.
Local media reports said the quake caused panic in North Sumatra's capital of Medan and other cities in the province. Electricity was cut in Medan.
People in some cities along the southeastern coast of Sumatra as well as Sinabang on Simeulue island and Gunung Sitoli on nearby Nias island poured into the streets and rushed to higher ground, reports said.