Staff writer, with Reuters

A magnitude 7.8 earthquake struck off the southern coast of Mindanao in the Philippines at 7:38am today, prompting the US Tsunami Warning System to issue an alert for neighboring countries, including Taiwan.The system issued a purple alert indicating a "tsunami threat."The potential threat zone includes Taiwan, the Philippines, Papua New Guinea, Yap and Palau.

A map shows the tsunami alert zone after a magnitude 7.8 earthquake hit the southern Philippines at 7:38am today.

Photo courtesy of the US Geological Survey

There ​were no immediate reports of major damage in the Philippines or Indonesia.The quake struck at a depth of 10km, said the German Research Centre for Geosciences, which had earlier pegged the earthquake at magnitude 8.2.