Two strong earthquakes hours apart struck a group of sparsely populated islands in the Luzon Strait in the northern Philippines early Saturday, killing at least eight people, injuring about 60 and causing substantial damage. The quakes collapsed houses built of stone and wood, arousing residents from sleep, said Roldan Esdicul, who heads the Batanes provincial disaster-response office.

"Our bed and everything were swaying from side to side like a hammock," Esdicul told The Associated Press by cellphone from Basco town, the provincial capital. "We all ran out to safety."

More than 1,000 residents of hard-hit Itbayat island — nearly half of the island's population of mostly fishermen — were advised not to return to their homes and stay in the town plaza as successive aftershocks shook the region, he said.

Get Breaking News Delivered to Your Inbox

"The wounded are still being brought in," Itbayat Mayor Raul de Sagon told a local radio station. He said more doctors may be needed if the number of injured from interior villages rises.

The Philippine seismology agency said the quakes measured 5.4 and 5.9. A third quake magnitude 5.7 struck later Saturday.

An Itbayat hospital was damaged but remained open. An air force helicopter and a plane were en route to Batanes to help ferry and provide aid to victims.

Itbayat, part of the Batanes Islands, has a population of about 2,800 people and lies in the Luzon Strait that separates the Philippines and Taiwan. The islands are famous for their stone-built houses, coral walls and cogon grass roofs.