A young girl and her grandmother were crushed to death when a wall fell in their house in Lubao town in Pampanga, a badly-hit province north of Manila, said provincial Governor Lilia Pineda.
Five people were killed when at least two buildings collapsed, a local official said.
Employees are seen at an open area in Manila, after an quake rocked the Philippines April 22, 2019.
"There are still some people inside but they [the rescuers] can't lift the debris that crashed down."
According to Philippine Institute of Volcanology and Seismology (Phivolcs) science research assistant Maila Advincula, as of 8 a.m. Tuesday, 491 aftershocks have been recorded close to the original source of the 6.1-magnitude quake.
Rescue teams in Manila were preparing to reinforce efforts to reach people trapped in Pampanga.
The quake was centred on the town of Castillejos, about 100 kilometres (62 miles) northwest of Manila, local geologists said.
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The Philippines' Department of Transportation earlier announced that operations at the airport would be suspended for 24 hours due to the damage.
Some people evacuated their offices in Manila.
Witness have described office buildings swaying in the main business district of the capital, Manila.
The U.S. Geological Survey's preliminary estimate is that more than 49 million people were exposed to some shaking from the natural disaster, with more than 14 million people likely to feel moderate shaking or more.
In July 1990, more than 2,400 people were killed on the northern island of Luzon in a magnitude-7.8 quake, one of the strongest tremors ever to hit the country.