A strong earthquake jolted Indonesia's northwest on Tuesday, but no tsunami warning was issued and there were no immediate reports of injuries or damage.

The 6.2 magnitude quake struck at a depth of 20 kilometres (12.5 miles) just off the coast of Simeulue island, west of Sumatra, according to the US Geological Survey.

Indonesia's weather and geophysics bureau said there was no tsunami threat.

People panicked and ran outside their homes when the quake hit. "We are now watching at the beach to monitor the movement of seawater," Simeulue resident Ahmadi told AFP. No casualties or infrastructure damage have been reported so far.