By Mikhail Flores and Karen Lema

MANILA, June 8 (Reuters) - The death toll in a powerful 7.8‑magnitude earthquake off the southern Philippine island of Mindanao on Monday has risen to at least 32 with dozens of people injured, disaster officials said, as Manila stepped up search and rescue operations.

The quake, which triggered tsunami warnings across several countries, hit early in the morning about 20 km (12.4 miles) off Sarangani province, with the tremors felt strongly across Mindanao and 420 km (261 miles) away in the city of Manado on the Indonesian island of Sulawesi.

The Philippines mobilised military and disaster response teams and authorities were verifying preliminary reports of 32 people killed and 134 injured across Mindanao, mostly from falling debris and landslides, according to civil defence officials.

Tsunami warnings were cancelled after more than six hours in the southern Philippines, northern Indonesia and the Malaysian state of Sabah on Borneo island, where residents in coastal areas had been told to evacuate immediately to higher ground.

The disaster came eight months after the Philippines suffered its deadliest tremor in 12 years, when a shallow 6.9 magnitude quake hit off the central island of Cebu, killing 79 people. Two powerful quakes struck Mindanao two weeks later, the strongest at a magnitude 7.4.

'WE WILL NOT LEAVE MINDANAO BEHIND,' PRESIDENT SAYS

President Ferdinand Marcos Jr ordered an immediate disaster response in Mindanao, an island the size of South Korea, with agencies directed to prepare relief supplies and evacuation centres and be ready for possible rescue operations.

"The national government is moving and we will not leave Mindanao behind," Marcos said in a statement.

The Philippines and Indonesia experience hundreds of quakes each year and sit on tectonically complex parts of the "Pacific Ring of Fire", a seismically active belt stretching from South America to the Russian Far East.

Damage to buildings, utilities and infrastructure was still being assessed, but the worst affected area was General Santos, a city of about 700,000 people, where shops and buildings were damaged, some with broken signs and glass, others reduced to piles of concrete and rubble.

Video shared by the local government showed the collapse of a building housing a fast food restaurant, with panicked onlookers fleeing as a cloud of dust spread quickly through the air.

One General Santos hospital was evacuated due to concerns about cracks on higher floors. One of the buildings at the city's Notre Dame of Dadiangas University collapsed, but no one was inside.

"I had to duck and shelter myself under the table. And it was very long and strong," the university's president Manuel de Leon told broadcaster DZMM.

STRONG AFTERSHOCKS ACROSS MINDANAO

The Philippine seismology agency said there were more than 200 aftershocks, at least nine of those strong and felt across Mindanao, the highest at a magnitude 6.7.

The quake struck just as schools were returning from a long break.

A video shared by one school the moment the quake struck showed a large group of children sitting on the floor swaying rapidly from side to side, some hugging teachers, before fleeing en masse as a makeshift shelter collapsed behind them.

Benjie Ancheta, police chief of Sarangani's Alabel town, said the quake occurred during a police flag-raising ceremony, causing some people to faint.

"This is the strongest earthquake we've experienced," Ancheta said by phone.

INDONESIAN ISLANDERS MOVE TO HIGHER GROUND

The U.S. Tsunami Warning System said multiple countries could be affected and Australia initially warned of potential tsunami waves on its northern coasts.

Japan's meteorological agency issued an advisory and said a tsunami of 0.2 m or lower had been observed, with some disruption to ferries and precautionary beach closures.

Witnesses in Indonesia's Manado said they felt the quake strongly. Only minor damage was reported, according to Abdul Muhari, spokesperson for Indonesia's disaster mitigation agency.

A tsunami with a wave height up to 0.75 m was detected in some regions in North Sulawesi, where people started moving to safer areas, including residents of the remote Sangihe Islands, among the closest to the Philippines.

(Reporting by Karen Lema, Mikhail Flores and Nestor Corrales in Manila, Gayatri Suroyo, Ananda Teresia and Fransiska Nangoy in Jakarta and Gnaneshwar Rajan in Bengaluru; Writing by Martin Petty; Editing by Jacqueline Wong, Tom Hogue, Neil Fullick and Kate Mayberry)

Posted by: Alma Angeles/NET25 News