Municipal workers checked a collapsed public building and a gym, both in the north of the island of Cebu, hours after the quake struck at sea off its northern tip at 9:59 pm (1359 GMT), provincial rescue official Wilson Ramos said.

"There could be people trapped beneath collapsed buildings," he told AFP, citing rescue efforts underway in the town of San Remigio and Bogo, a city near the epicentre with 90,000 residents. He said he did not know how many people are missing.

Recovery efforts were being hampered by the dark as well as aftershocks, he added. The US Geological Service has recorded four quakes of magnitude 5.0 or higher in the area following the first tremor.

The local seismology office warned of a possible "minor sea-level disturbance" and urged residents of the central islands of Leyte, Cebu and Biliran to "stay away from the beach and not to go to the coast".

Cebu firefighter Joey Leeguid told AFP from San Fernando town: "We felt the shake here in our station, it was so strong. We saw our locker moving from left to right, we felt slightly dizzy for a while but we are all fine now."

Martham Pacilan, a 25-year-old resident of the resort town of Bantayan, also near the epicentre, said he was at the town square near a church, which was damaged by the quake.

"I heard a loud booming noise from the direction of the church then I saw rocks falling from the structure. Luckily no one got hurt," he told AFP.

"I was in shock and in panic at the same time but my body couldn't move, I was just there waiting for the shake to stop."

- Power outage -

Agnes Merza, a carer based in Bantayan, said her kitchen tiles had cracked.

"It felt as though we would all fall down. It's the first time I have experienced it. The neighbours all ran out of their homes. My two teenage assistants hid under a table because that's what they were taught in the boy scouts," the 65-year-old told AFP.

The Cebu provincial government reported a commercial building and a school in Bantayan had collapsed, while a number of village roads had also sustained damage.

The quake caused power lines to trip, leading to outages across Cebu and nearby central islands, the National Grid Corp. of the Philippines said in an advisory, adding it was still assessing the extent of the damage.

In a live video message on her official Facebook account, Cebu provincial governor Pamela Baricuatro urged residents to "stay calm and move to open areas; keep away from walls or structures that may collapse and stay alert for aftershocks."

She said the provincial government was assessing the situation and reaching out to municipal officials.

The USGS had reported a magnitude reading of 7.0, before revising it down, while the Pacific Tsunami Warning Center said there was no tsunami threat from the earthquake.

Quakes are a near-daily occurrence in the Philippines, which is situated on the Pacific "Ring of Fire", an arc of intense seismic activity stretching from Japan through Southeast Asia and across the Pacific basin.

Most are too weak to be felt by humans, but strong and destructive ones come at random, with no technology available to predict when and where they might strike.