A magnitude 6.9 earthquake rattled the southern Mindanao region of the Philippines on Friday, German Research Center for Geosciences (GFZ) said.

The quake struck off the shore of the Mindanao region, at a depth of 10 kilometres (6.2 miles), GFZ added. The Pacific Tsunami Warning Center said no tsunami was expected.

There were no immediate reports of casualties. Philippines’ seismology agency said the quake lasted several seconds and advised residents to be on alert for aftershocks and damage.

Radio announcer Leny Aranego of General Santos city in South Cotabato said the strong earthquake damaged walls and toppled some computers from desks.

“We saw how the walls cracked and computers fell,” Aranego told DZRH radio station.

Passengers at an airport in General Santos City were evacuated to the tarmac, said Michael Ricafort, was about to board a plane to Manila when the quake hit.

The Philippines lies on the “Ring of Fire”, a belt of volcanoes circling the Pacific Ocean that is prone to seismic activity.