(Reuters) - A major earthquake of 7.7 magnitude struck off the coast of Aceh on the Indonesian island of Sumatra on Wednesday triggering panic and power blackouts, although a tsunami alert was later lifted.Neighboring Thailand and Malaysia, lying east of Sumatra, also canceled tsunami warnings.A Reuters photographer in Sinabang on Simeulue island, south of Aceh, said that electricity was cut in the area and that he saw four injured people, including a child with a head wound who had been hit by fallen masonry.
Aceh Governor Irwandi Yusuf said earlier there had not been reports of damage or casualties so far.
"I am on the coast now, some people had gone to take refuge on higher ground but now they have returned to their homes," Yusuf told Metro TV.
The resource-rich island of Sumatra is an important supplier of commodities such as rubber, palm oil and liquefied natural gas (LNG), but there were no immediate reports of delays in shipments because of the quake.
The quake, which struck around 5:15 a.m. (2215 GMT), was centered 200 km (125 miles) west-northwest of the coastal town of Sibolga and was at a depth of 31 km, the U.S. Geological Survey said. The epicenter was around 215 km from Medan, the largest city on Sumatra.
There were at least three aftershocks after the initial major quake.
ELECTRICITY POLES SWAY
The Hawaii-based Pacific Tsunami Warning Center initially warned the quake could generate a local tsunami, but later canceled its tsunami watch, saying: "Sea level readings indicate that a significant tsunami was not generated."
An official from Indonesia's meteorology agency said a tiny tsunami of only 3 cm (1 inch) had been detected at Sinabang and lifted its own tsunami warning.
A Metro TV reporter in the Sibolga area of North Sumatra said that he fell off his motorbike when the quake struck and the force left electricity poles swaying for minutes afterwards.
Tremors from the quake were felt in Dumai, in Sumatra's Riau province about 1,100 km from the epicenter, Indonesia's Antara news agency reported.
Hamid Sarong, a resident of Aceh's provincial capital Banda Aceh, which was devastated by a tsunami in 2004, said that the quake was felt while people in the staunchly Muslim province were at dawn prayers, although there was no panic.
Sumatra lies along the Pacific "Ring of Fire", one of the world's most active seismic faultlines, and is frequently hit by earthquakes.
In December 2004, a magnitude 9.15 quake off Aceh triggered an Indian Ocean tsunami that killed about 226,000 people in Indonesia, Sri Lanka, India, Thailand and nine other countries.
A 7.6 magnitude quake struck last September off the city of Padang, southeast of Wednesday's epicenter, killing more than 1,000 people.