The quake off the coast of the island of Mindanao had a depth of 30 kilometres (18.6 miles), the USGS added.
The Philippine Institute of Volcanology and Seismology placed the epicentre about 43 kilometres southwest of the town of Maitum, located in a mountainous and sparsely populated area.
Local authorities told AFP early indications were that the quake had caused no significant damage.
"It was strong but didn't last long. We have checked but it was negative (for damage or casualties)," said Gilbert Rolifor, a fire department official in Maitum.
Quakes are a daily occurrence in the Philippines, which sits along the Pacific "Ring of Fire", an arc of intense seismic and volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.
Most are too weak to be felt by humans, but strong and destructive quakes come at random with no technology available to predict when and where they will happen.
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