MANILA -- The cost of damage to infrastructure due to a powerful quake that rattled Luzon nearly a week ago has hit half a billion pesos, the country's disaster agency said Sunday.

The magnitude 6.1 quake during the afternoon rush hour last Monday had set buildings swaying in the capital, shuttered the Clark Airport for 48 hours, and flattened a supermarket to the ground in the agricultural town of Porac, Pampanga.

Around P505.9 million worth of damage in 334 structures was tallied in Metro Manila, and the Ilocos, Central Luzon, and Calabarzon regions, said the National Disaster Risk Reduction and Management Council in a 6 a.m. report.

Central Luzon was worst hit, suffering P222.6 million worth of damage to schools, and P200 million from roads and bridges, the report said.

Monday's quake killed 18 people, injured 174 others and left 5 missing, it added.

Less than 24 hours later, a magnitude 6.5 tremor rumbled across Visayas, injuring at least 5 people but spawning no major damage to property.

The 2 tremors were unrelated and could not cause movement in the West Valley Fault that may generate a magnitude 7.2 quake, said state seismologists.

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The Philippines straddles the Pacific "Ring of Fire", an arc of intense seismic activity that stretches from Japan through Southeast Asia and across the Pacific basin.