(1st UPDATE) A magnitude 6.1 earthquake struck Luzon Monday afternoon, forcing people to flee from buildings in Metro Manila and nearby areas.
The tremor struck near Castillejos, Zambales at a depth of 21 kilometers, Phivolcs said.
It was initially reported at magnitude 5.7 but was upgraded by Phivolcs to magnitude 6.1.
The earthquake could have originated from either the Manila Trench or a fault line in Zambales, Phivolcs Undersecretary Renato Solidum told dzMM Teleradyo.
The earthquake was also felt in the following areas:
Intensity V -San Felipe, Zambales; Malolos and Obando, Bulacan; Quezon City; Lipa, Batangas; Manila City; Abucay, Bataan; Valenzuela City; Magalang, Pampanga
Intensity IV - Pasig City; Makati City; Caloocan City; Meycauayan and San Jose Del Monte, Bulacan; Floridablanca, Pampanga; Villasis, Pangasinan; Tagaytay City; Villasis, Pangasinan;
Baguio City; Marikina City; Las Pinas City
Intensity III - Dasmarinas, Indang and Gen. Trias, Cavite; Lucban, Quezon; Muntinlupa City, Cabanatuan City; Palayan City; Gapan City; Santo Domingo and Talavera, Nueva Ecija
Intensity II - Baler, Aurora
Solidum said this is not a major earthquake, but was felt because it was a bit shallow.
"This earthquake is not a major earthquake but it's a strong earthquake, but this is already far from Metro Manila but a little bit shallow so we can feel it," Solidum told ANC.
There is also no tsunami warning as the epicenter is on land, Solidum added.
The tremor is expected to cause damage and trigger aftershocks.