In the city of Batac in the neighbouring province of Ilocos Norte, several patients spent most of the night outside a government hospital after the ceiling collapsed on several rooms and damaged equipment, hospital staff said.
Boulders rolling down a hillside temporarily blocked a road linking Batac to the nearby town of Banna, but rescue officials said the landslide had since been cleared.
A number of old churches in Abra and Ilocos Norte also sustained damage, the civil defence office said.
Ilocos Norte governor Matthew Manotoc declared a school holiday and government workers were told not to report for work as the authorities inspected the integrity of buildings.
In July, a 7.0-magnitude quake also in mountainous Abra province triggered landslides and ground fissures, killing 11 people and injuring several hundred others, according to the official count.
Quakes are a daily occurrence in the Philippines, which sits along the Pacific “Ring of Fire”, an arc of intense seismic as well as volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.