The US Geological Survey said the quake struck underneath the island of Bohol, in a region popular with tourists.
People were killed as buildings and markets collapsed in Bohol and nearby Cebu province. Several buildings and churches were damaged by the quake.
The quake struck at 08:12 (00:12GMT) on a national holiday in the country.
Officials say that most of those killed were in Cebu, considered the second major city in the country.
At least five people died when part of a fishing port collapsed, reports the Associated Press (AP) news agency. Two more people died and others were injured when a roof at a market fell, AP adds.
Neil Sanchez, head of the Cebu disaster management office, told broadcaster ABS-CBN that they were trying to confirm reports that a school had collapsed.
“Communication lines are quite difficult here,” he said. “Even the disaster risk reduction management office has been damaged. We had to move elsewhere.”
Edgardo Chatto, the governor of Bohol, said that a church and a city hall building were damaged.
The tremor triggered power outages in parts of the province, local media reported.
British man David Venables, who has lived in Cebu for seven years, said it was the strongest quake he had experienced.
“It’s a very strange and frightening experience when the very foundations of the house and surrounding area shake uncontrollably,” he said.
Bonita Cabiles, a resident of Mandaue city in Cebu province, told the BBC said she was woken up when she felt the ground rumbling.
She said there was a lot of structural damage in the area, including to the bell tower of the Santo Nino church in Cebu, one of the most well-known churches in the country.
It was fortunate that it was a national holiday and the students were not in school, she said.
Straddling the so-called Ring of Fire belt of seismic activity, the Philippines often experiences earthquakes.
In August 2012 a 7.6-magnitude earthquake struck off the eastern Philippine island of Samar, causing tsunami evacuations and power cuts.