MANILA -- A strong earthquake struck the coast off Sarangani Island in Davao Occidental Tuesday night, according to the Philippine Institute for Volcanology and Seismology.

Phivolcs said that the magnitude 6.3 quake struck the waters 295 kilometers southeast of Sarangani Island in Davao Occidental at 6:17 p.m. on April 22.

The undersea quake, which was tectonic in origin, hit at a depth of 117 kilometers.

Intensity III was felt in Malungon, Sarangani and the City of General Santos.

According to Phivolcs, Intensity III is "felt by many people indoors especially in upper floors of buildings. Vibration is felt like one passing of a light truck. Dizziness and nausea are experienced by some people. Hanging objects swing moderately. Still water in containers oscillates moderately."

The tremblor was also felt at Intensity II in Tupi and Koronadal City in South Cotabato, and Kiamba in Sarangani.

Intensity I was likewise felt in Maitum and Malapatan in Sarangani, and Palimbang in Sultan Kudarat.

The following instrumental intensities were also recorded:

Intensity III - Malungon, Sarangani

Intensity II - Kiamba, Sarangani; City of General Santos; Tupi and City of Koronadal, South Cotabato; Nabunturan, Davao de Oro

Intensity I - Maasim and Alabel, Sarangani; City of Kidapawan, Cotabato; Santo Niño, Banga, T'Boli, Lake Sebu, and Surallah, South Cotabato; City of Davao;

Magsaysay and Matanao, Davao del Sur; Don Marcelino, Davao Occidental; Lambayong, Sultan Kudarat

Damage and aftershocks may be expected, Phivolcs said.