A MAGNITUDE 6.6 earthquake struck central Mindanao on Tuesday morning, the second major tremor to hit southern Philippines this month, geologists said.

The quake killed at least four people, based on reports from the Philippine News Agency and the local disaster agency.

The shaking lasted up to a minute in some places, damaging homes, buildings and roads in a region where hundreds were still reeling from a quake that killed at least five earlier this month, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).

The Philippines lies in the so-called Pacific “Ring of Fire,” an arc of intense seismic activity around the Pacific Ocean where most of the world’s earthquakes strike.

A teenage boy died after he was crushed by falling debris as he tried to escape his school in Magsaysay town in Davao del Sur, the state news agency said. A man also died after he was hit by concrete blocks at their church where he was working, it said.

Meanwhile, the National Disaster Risk Reduction and Management Council in a report said a father and his son from Arakan town in Cotabato also died in the quake.

Tuesday’s quake, which was followed by several aftershocks, had its epicenter in Tulunan, Cotabato, the same area where a 6.3 earthquake struck on Oct. 16, based on monitoring by the state volcano agency.

The quakes were not expected to spawn a tsunami because these were “inland,” but more aftershocks were expected, Phivolcs chief Renato U. Solidum, Jr. said at a briefing livestreamed from Manila.

“We need to watch out for aftershocks and it is important that we do not panic,” he said in Filipino. Mr. Solidum said Tuesday’s tremors were related to the Oct. 16 earthquake.

Power lines were affected in several areas but the Mindanao transmission backbone “remains intact,” the National Grid Corp. of the Philippines said in a statement.

The Civil Aviation Authority of the Philippines said no damage was reported in all Mindanao airports, including terminals, runways and other facilities.

The main airports are in Butuan, Davao, Cotabato, General Santos and Laguindingan, while satellite airports are in Ozamiz, Camiguin and Iligan.

In Davao City, one of the most urbanized and populous areas, major cracks and some damage were reported by several shopping malls, schools and other public infrastructure.

Davao City and most local governments that felt the earthquake suspended classes, and at least three suspended work to give way to building inspections.

Cotabato Vice Governor Emmylou T. Mendoza called on local governments and the private sector to suspend school and work “if necessary.” — with a report from Maya M. Padillo