The epicenter of the earthquake was about 11km (7 miles) east-southeast of the town of Dolores, the United States Geological Survey said.
Videos and pictures posted on social media by local officials and residents showed some buildings collapsed into rubble with others leaning precariously, their windows shattered.
Many cars were crushed by the debris and roads were left crumpled and damaged.
“Several houses and infrastructures in different locations are severely damaged after a 7.0 magnitude earthquake shook Luzon this morning,” Philippine Red Cross said on Twitter.
⚠️ EARTHQUAKE UPDATE ⚠️
Several houses and infrastructures in different locations are severely damaged after a 7.3 magnitude #earthquake shook #Luzon this morning.
????: PRC Ilocos Sur Chapter, PRC Abra Chapter#AlwaysFirstAlwaysReadyAlwaysThere#PRCLifelineOfThePeople #Lindol pic.twitter.com/cZYxukLFEL
“All Philippine Red Cross Chapters are directed by PRC Chairman and CEO @DickGordonDG to continuously assess the situation and damages to their areas of responsibility hours after the big earthquake,” it added.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said that there is no tsunami threat to the Philippines after the quake. (ILKHA)