Stay-at-home orders are now in effect in Manila and four surrounding provinces on the island of Luzon.
The Philippines only just emerged from a long lockdown in June.
But hospitals have been struggling to cope with a five-fold rise in confirmed infections, now surging past 100,000.
The lockdown means a return to stay-at-home orders except for going out to buy essential goods or exercising outdoors. Public transport will also be suspended and domestic flights are grounded, while restaurants are restricted to takeaways.
The new restrictions took effect on Tuesday and will last for two weeks.