MANILA - Eight people were killed and over 60 hurt when two powerful earthquakes, just hours apart, struck the Philippines' northernmost province early on Saturday (July 27) morning.

The first tremor, a magnitude 5.4, struck Batanes, a group of sparsely populated islets north of the main island of Luzon, at 4am.

A second, stronger quake - recorded at magnitude 5.9 - then struck at 7.30am.

Both were at relatively shallow depths.

Mr Ricardo Jalad, executive director of the National Disaster Risk Reduction and Management Council (NDRRMC), said in a bulletin eight people died.

"They were hit by rubble and debris, not buried," he told reporters.

A Facebook video posted by the Philippine Daily Inquirer showed volunteers pulling a man out of a pile of boulder-size rocks and wood.

The hardest hit was Itbayat, an island town with a population of close to 3,000 that is nearer Taiwan's southernmost tip than Luzon.

Police Sergeant Uzi Villa told Agence France-Presse many in the town were still asleep when the first quake struck.

"Some people died because they were sleeping soundly since it was still early… We saw houses shaking. Some of the walls of the houses collapsed and fell on the victims," he said.

Mr Obet Nico, a village watchman in Itbayat, told CNN Philippines he was with two guests when the first quake struck.

"It didn't last long, and it wasn't really that strong. But there were rocks falling near us," he said.

But when the second, stronger tremor hit, many of the old houses, weakened by the first quake, collapsed.

"It was so strong we fell off our motorcycle," said Mr Nico.

Photos and videos posted on Twitter showed walls of homes giving way, roofs caving in, and rubble by the roadside.

The initial quake caused a deep crack around the steeple of Itbayat's 19th-century church, a popular tourist attraction. The belfry then collapsed onto a lawn when the second temblor hit the island.

The first floor of a two-storey school building had deep gashes and crumbling cement throughout its walls.

Patients at a local hospital were evacuated. They were taken first to a public park, and then crammed into a covered basketball roof when it began to rain.

"Most of the houses destroyed were old and made of limestone," Mr Dan Esdicul, NDRRMC's head in Batanes, told radio station DZMM.

Batanes, which sits along the path of many tropical storms and cyclones that cross the Philippines, is known for ancestral homes famed for being storm-resilient.

These old houses are made of limestone and coral walls a metre thick. Roofs consist of concrete slabs or cogon wrapped in fishing nets and supported by bamboo beams.

Though crude, these homes could withstand gales of up to 250kmh, but apparently not against a pile-up of strong earthquakes.

"We were not prepared for this," said Itbayat Mayor Raul de Sagon.

As the quake jolted Batanes, thousands were roused from their sleep during pre-dawn earthquake drills all around metropolitan Manila.

Some journalists had asked why the drills needed to be held so early in the morning, said Mr Renato Solidum, a prominent seismologist and disaster-response expert. He said the Batanes quake helped officials underscore the fact that a disaster could strike anytime.

The Philippines is part of the Pacific "Ring of Fire", an arc of intense seismic activity that stretches from quake-prone Japan through South-east Asia and across the Pacific basin

A 6.3-magnitude earthquake rocked large parts of Manila and north of it in April, killing at least 11, emptying buildings of tens of thousands who have just returned from the long Holy Week holiday, and shutting down rail lines and a key airport.

A magnitude 7.7 quake killed nearly 2,000 people in the northern Philippines in 1990.