A moderate 5.6-magnitude earthquake struck the Indonesian island of Sumatra today, the US Geological Survey(USGS) said, but there were no immediate reports of damage.

The quake hit at 4.55 am (7.55am AEDT today) 95 kilometres east-southeast of the city of Padangsidempuan in North Sumatra at a relatively deep 213km, USGS said.

Indonesia is battling the aftermath of a volcanic eruption in central Java that has killed more than 270 people and a tsunami off western Sumatra, triggered by an undersea quake, which killed 428 in October and left tens of thousands homeless.

Indonesia sits on the Pacific "Ring of Fire", where the meeting of continental plates causes high seismic activity.