A powerful earthquake struck the southern Philippines Tuesday, killing six people, cracking buildings and injuring dozens in a region still reeling from a previous deadly tremor.

Terrified locals ran into the streets after the 6.6-magnitude quake, which hit the island of Mindanao as schools and offices opened for the day.

The shaking lasted up to a minute in some areas, damaging homes, multi-storey buildings and classrooms in a region where hundreds are still displaced by a quake that killed at least five earlier this month.

The Philippines suffers regular tremors as part of the Pacific "Ring of Fire", an arc of intense seismic activity that stretches from Japan through Southeast Asia and across the Pacific basin.

A teenage boy was crushed by a falling wall as he tried to escape his school in Magsaysay, the town spokesman told AFP. Though other students were injured in a "stampede" to escape the building, they survived.

Rock and landslides unleashed by the violent shaking killed four others, while a collapsed wall crushed a man, authorities said.

At least 50 people were hurt by falling debris, including some seven pupils and teachers hurt escaping their collapsed elementary school. Locals were awed by the power of the quake, which was shallow and thus potentially more destructive.

"Buildings were not just moving, they were swaying," Gadi Sorilla, a doctor at a hospital in Tulunan, a town about 25 kilometres (15 miles) from the epicentre told AFP.

Rescue teams worked until dark on Tuesday to assess the damage to the region, where electricity and phone services were knocked out in some areas by the power of the quake. The US Geological Survey said the initial 6.6 magnitude quake was followed by a number of smaller shakes, including one measuring 5.8.

Copyright Agence France-Presse, 2019