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, but there were no immediate reports of damage. The US Geological Survey said the quake, initially reported as a magnitude 6.5, struck at 6:53 am (22:53 GMT on Friday) and was centred 114 km (71 miles) east of Davao on Mindanao.