JAKARTA ~ A 5.5-magnitude earthquake struck at sea off Aceh province on Monday but there was no threat of a tsunami and no immediate reports of damage, geologists said.

The epicenter of the quake, which hit 30 kilometers deep and struck at 11:44am, was 50 kilometers southwest of the town of Sinabang, the main town on Simeulue island.

“The quake was felt only in Sinabang town; there’s no report of damage so far,” geophysicist Agung Mulyo Utomo said.

The US Geological Survey logged the quake at a similar magnitude.

Indonesia was the nation worst hit by the earthquake-triggered Asian tsunami in December 2004 that killed 168,000 people in Aceh.

The archipelago sits on the so-called Pacific Ring of Fire, where continental plates meet, causing seismic and volcanic activity.