An offshore 7.8-magnitude earthquake rocked southern Philippines on Monday, killing at least 32 people, injuring more than 200 and triggering tsunami warnings across several countries.

The tremor struck early in the morning as schools were reopening after a long summer break. The epicentre was 20km off Sarangani province on the island of Mindanao, and the jolt was felt around 420km away on the Indonesian island of Sulawesi.

The country’s seismology agency said at least nine strong aftershocks were felt across Mindanao on Monday morning, the highest at a magnitude of 6.7. The full extent of the ‌damage was not yet clear and authorities said assessments were underway.

The city of General Santos bore the brunt as buildings collapsed and critical infrastructure sustained damage, with videos showing panicked residents fleeing as clouds of dust spread quickly through the air. The port city, home to more than 700,000 people, is a hub for the tuna industry.

“It’s a major earthquake and we’re expecting damage,” Teresito Bacolcol, the director of the Philippine Institute of Volcanology and Seismology, said.

Tsunami damage was reported in one Philippine village and smaller waves were measured in Indonesia, Palau and as far away as southern Japan. Six shanties on stilts were damaged in Zamboanga del Sur due to the tremor and taller waves, officials said.

Tsunami alerts were issued in the southern Philippines, northern Indonesia and in the Malaysia state of Saba on Borneo island.

The Pacific Tsunami Warning Center said the threat of a tsunami largely passed about five hours after the earthquake.

At least seven people were killed and 130 injured in General Santos, where a few buildings collapsed and several structures, including a key access bridge, sustained dangerous cracks, said Rod Sosmeña, regional director of the Office of Civil Defence.

The rest of the deaths occurred in the southern provinces of South Cotabato and Davao Occidental and on Balut Island, mostly due to falling debris and a landslide.

A General Santos hospital was evacuated after cracks appeared on its higher floors while a building at the city’s Notre Dame of Dadiangas University collapsed.

“I had to duck and shelter myself ⁠under the table. It was a very long and strong earthquake,” university president Manuel de Leon told local broadcaster DZMM.

The airport in General Santos was temporarily shut and 17 domestic flights were cancelled, civil aviation officials said. “Our pickup truck suddenly jerked and I thought we had a flat tire,” said Mr Sosmeña, who was traveling as the quake struck at 7.37am. “People dashed out of houses into the streets.”

The natural disaster hit eight months after the Philippines suffered its deadliest tremor in 12 years, when a shallow 6.9-magnitude quake hit off the island of Cebu, killing 79 people.

The Philippines and neighbouring Indonesia experience hundreds of earthquakes each year as they sit on tectonically complex areas of the Pacific Ring of Fire, a seismically active belt stretching from South America to the Russian Far East.

Mr Sosmeña said authorities were checking reports of some students being trapped in a two-story school that collapsed in General Santos. He could not immediately provide details, but the national police said at least seven people were missing in the city.

The Bureau of Fire said without elaborating it was involved in search and rescue work at a damaged building and a warehouse in General Santos.

Public schools had just reopened nationwide after the summer vacation from April to May. An official said almost 100 students attending morning flag-raising ceremonies in his southern region sustained bruises and some fainted in panic.

Benjie Ancheta, police chief of Sarangani’s Alabel town, said some people fainted at a police flag-raising ceremony as well.

“This is the strongest earthquake we've experienced,” he said.

Philippine president Ferdinand Marcos Jr said “the national government is moving and we will not leave Mindanao behind”.

Malaysian prime minister Anwar Ibrahim said his government was ready to assist the Philippines. “I pray for the safety and wellbeing of all those affected, wishing them strength and courage in the difficult days ahead,” Mr Anwar said on X.