A magnitude-6.6 quake struck off Indonesia's Sumatra island, the US Geological Survey reported on Wednesday.

The quake, quite shallow at a depth of 26.6 miles (42 km), struck 130 miles (209 km) northwest of the Sumatra town of Bengkulu at 3:01 a.m. on Thursday (2001 GMT on Wednesday).

It followed a magnitude-5.5 earthquake in the same area two and a half hours earlier.