2 strong quakes shake Sumatra

The first quake, measured at 6.0, was centred 364 kilometres south of Banda Aceh, capital of Aceh province, the USGS said.

It struck at 3:54 am (2054 GMT Friday) with a depth of 10 kilometres.

The second quake, measured at 5.1, struck at 13:15 pm (0615 GMT) and was centred 69 kilometres southeast of Sinabang island, off western Sumatra, said the Indonesian National Earthquake Center in Jakarta.

Both readings were based on the open-ended Moment Magnitude scale, now used by US and other seismologists, which measures the area of the fault that ruptured and the total energy released.

"We received no reports of damages or casualties caused by the quakes but they were felt by residents in several towns on Sumatra island," the centre's Budi Waluyo told AFP.

A massive 7.7-magnitude earthquake earlier this month triggered a tsunami that lashed the south coast of Indonesia's Java island, killing more than 600 people.