More than 200 people were also injured in Aceh's remote, mountainous interior when the strong 6.1-magnitude quake struck on Tuesday, flattening buildings and triggering landslides.
The quake, which struck at a shallow depth of just 10 kilometers (six miles), has sparked panic in the natural disaster-prone region where more than 170,000 people were killed by the quake-triggered tsunami of 2004.
In Blang Mancung village, Central Aceh district, at least six children were killed when a mosque collapsed during a Koran reading session.
Subhan Sahara, head of the district's disaster agency, previously said a further 14 children were trapped in the collapse. But on Wednesday he said rescuers had not yet found any more bodies in the rubble and were now unsure how many had been inside.
"This is the biggest earthquake we've ever had here," he told AFP.
"People are still frightened, especially after the aftershocks last night. Nobody dared to stay at home. Everyone slept on the roads or in car parks.
"The earthquake triggered many landslides. People could not get out of the area because of fallen trees and mounds of earth blocking roads."
The main hospital in the district was overwhelmed and tents had been set up in the building's car park to treat the flood of patients, he said.
Military, police and local government officials were trying to head to other affected areas on Wednesday by ground and in aircraft but some roads were blocked by landslips, the national disaster agency said.
The agency dispatched a helicopter from neighboring Riau province to assist in rescue efforts, while an air force plane was also deployed to assess the damage.
"So far 22 people died, 210 people were injured, and thousands of buildings and homes were damaged in the quake," disaster agency spokesman Sutopo Purwo Nugroho said.
The casualties were spread over the two worst-hit districts of Central Aceh and Bener Meriah, he said. Scores of people were being treated at hospitals across the region.
In Bener Meriah, about 300 people camped out overnight in open spaces, such as football fields, as the area was hit by strong aftershocks, Fauzi, an official from the local disaster agency told AFP.
He said many were in desperate need of food.
People ran outside in the provincial capital Banda Aceh as the quake -- some 320 kilometers (200 miles) away -- shook houses, and in Medan city to the south of the province on Sumatra island.
Aceh, on the northern tip of Sumatra, is regularly hit by quakes. The huge quake-triggered tsunami of 2004 not only killed tens of thousands in the province, but also many in countries around the Indian Ocean.