Davao: A strong earthquake of magnitude 6.3 struck off the Philippine's Mindanao island on Saturday, sending hotel guests and construction workers running from buildings in Davao.

The US Geological Survey said the quake, initially reported as a magnitude 6.5, struck at 6.53am (8.53am AEST) and was centred 114 km east of Davao on Mindanao.

The quake hit off the cost of the Philippines close to Davao, the hometown of Philippine President Rodrigo Duterte. Credit:USGS

It was a deep tremor, 69 km below the seabed, and was not expected to cause a tsunami, the Pacific Tsunami Warning Centre said. There were no immediate reports of damage

A magnitude 6.3 quake is considered strong and is capable of causing severe damage, but Renato Solidum, head of the Philippines' seismic agency, said the effects of this one would be mitigated by its location and depth.