SURIGAO CITY: Rescuers dug through rubble Saturday to find survivors after a powerful earthquake struck the southern Philippines, killing at least four people and sending thousands fleeing for safety.

Residents of the southern town of Surigao in Mindanao island spent the night huddled in fear as aftershocks rocked the city following the 6.5-magnitude quake which struck late Friday when many people were already in bed.

Provincial governor Sol Matugas told DZMM radio on Saturday that at least four people had died in the disaster.

"There was one person buried alive in his home," the governor said.

Three others, including a four-year-old boy, were killed by falling debris, civil defence personnel said.

At least 75 people were injured, mostly by falling objects, with 14 in critical condition, they added.

Regional civil defence chief Rosauro Arnel Gonzales said several houses had collapsed and search and rescue teams had been dispatched to make sure no one was inside.

"There are reports of houses that were damaged and they (the rescue teams) have to go around these impacted areas to really ascertain whether there is a need to conduct rescue," he told AFP.

The disaster knocked out power in Surigao City and surrounding areas with electrical supplies only partially restored by Saturday.

The quake damaged many buildings, including in the two-storey Gaisano mall -- one of the city's largest structures -- and shattered windows, sending sharp shards and heavy rubble into the street.

"I thought it was the end of the world. The cement on the roads was cracking open," resident Carlos Canseco told ABS-CBN television.

One bridge collapsed and two others were damaged in the quake, which also cracked the city airport's runway, forcing flights to be diverted, the civil defence office added.

Terrified residents fled to higher ground after the quake, fearing that a tsunami would hit the coastal city of over 152,000 people.

Others spent the night in parking lots and open fields.

Hospital staff temporarily brought bed-ridden patients outside until the aftershocks eased.

Provincial disaster monitoring chief Ramon Gotinga said residents were still on edge.

"They are all still traumatised. At the slightest shaking, they run out in the streets," he said.

The Philippines lies on the so-called Ring of Fire, a vast Pacific Ocean region where many earthquakes and volcanic eruptions occur.

The last lethal quake that hit the country measured 7.1-magnitude. It left over 220 people dead and destroyed historic churches when it struck the central islands in October 2013. -AFP