A strong 6.1-magnitude earthquake struck Indonesia's northwestern province of Aceh today, causing buildings to collapse and injuring at least 50 people.

The quake hit inland at 0737 GMT at a depth of just 10 kilometres, 55 kilometres south of Bireun and 72 kilometres southeast of Reuleuet, the US Geological Survey said.

"We have received around 50 people with injuries suffered when the walls of their houses collapsed," Ema Suryani, a doctor at a health clinic in Lampahan city, Bener Meriah district, told AFP.

"The injuries vary from open wounds to broken bones." Injured people had been transported from several affected villages in two trucks, she said. People also ran out of buildings in panic in the provincial capital Banda Aceh as the quake shook houses for around one minute, an AFP journalist at the scene said.

A massive quake struck off Aceh in 2004, sparking a tsunami that killed 170,000 people in the province on Sumatra and tens of thousands more in countries around the Indian Ocean. Indonesia sits on the Pacific "Ring of Fire" where continental plates collide, causing frequent seismic and volcanic activity.