"A boy was killed and another person was seriously injured," Indonesian National Disaster Management Agency spokesman Sutopo Purwo Nugroho said.
Falling debris killed the boy as he slept in his home in Subulussalam, Aceh province, a doctor said.
"The boy was sleeping next to his mother when a wall collapsed and bricks fell onto his stomach, crushing him. His mother brought him to us but we couldn't save him in time," the doctor, named Hasbi, said.
Panicked residents rushed out of their homes, many crying and screaming for help, as the quake shook the area for around two minutes, an AFP correspondent said.
"That was the strongest quake I'd ever felt. I thought the end of the world was here," 42-year-old farmer Abdul Kader Angkat said.
The jolt was also felt by residents in the cities of Banda Aceh and Medan, officials said.
The Hawaii-based Pacific Tsunami Warning Center said the quake was too far inland to generate a tsunami.
Indonesia sits on the Pacific "Ring of Fire", where the collision of continental plates causes high seismic activity.
Aceh was devastated when a 9.1-magnitude quake off Sumatra in December 2004 triggered a huge tsunami that killed more than 220,000 people around the Indian Ocean.