The Philippines has tightened restrictions in the community and at the borders, as it confirmed the start of a new wave of Covid-19 infections - this time fuelled by the highly contagious Delta variant.

The government yesterday announced that its travel ban would now include Malaysia and Thailand. It has already denied entry to travellers from Indonesia and most of South Asia.

Shelter-at-home and movement curbs in Metro Manila have been stepped up a notch to a "general community quarantine with heightened restrictions" till July 31 at least.

This means fewer people will be allowed to dine out or go to churches for mass, weddings, baptisms and other religious services.

Gyms, salons, barbershops, tourist attractions and meeting venues will again be shut.

Social gatherings in homes, such as birthday parties and reunions, are banned.

The health ministry confirmed late on Thursday what independent researchers and local government officials had been saying for days - that there is already local transmission of the Delta variant.

"Clusters of Delta variant cases were seen to be linked to other local cases, therefore exhibiting local transmission," it said in an advisory.

The Philippines had previously largely sidestepped the Delta-fuelled surges that have plagued neighbouring countries.

But data analysts from independent group Octa Research said a new wave of Covid-19 cases was already "in its early stages" in the Philippines.

Metro Manila, home to some 13 million, is now experiencing an uptick in new cases. The average number of new infections per day was 813 in the past week, up from 638 the week before.

The health ministry said it has been preparing the healthcare system for a new wave of infections, adding more hospital beds and quarantine sites, and beefing up supplies of oxygen, ventilators and medication.

But Octa is pressing the government to do more.

"Let us not wait for the numbers to explode before we act… At the very least, the (government) must contemplate a stricter quarantine status or impose more restrictions in (Metro Manila)," it said.

If the Delta variant is driving the current surge, the group added, "we need to crush it with lockdowns (localised and regional)".

The Alpha and Beta variants, first found in Britain and South Africa respectively, are still the dominant strains in the Philippines, with close to 3,500 cases out of 7,579 samples taken for genome sequencing.

Only 47 cases of the Delta variant have been found so far, but it has already surfaced in Metro Manila, a sprawling, densely populated region of 16 cities.

Experts believe that the Delta variant is behind crippling surges in places outside Manila, including Davao City, President Rodrigo Duterte's home turf, where sweeping lockdown measures in recent weeks have failed to bring down infection numbers.

Octa reported that the reproduction rate of the coronavirus in Metro Manila has gone up to 1.15.

The acceptable number is 1 or below. At that rate, cases could climb to 8,000 to 10,000 in the coming weeks.

Health Undersecretary Maria Rosario Vergeire said yesterday that the government was ready to fall back into "granular lockdowns" if hospitals start to get overcrowded with Covid-19 patients again.

With more than 1.5 million cases and close to 27,000 deaths, the Philippines has the second-worst coronavirus outbreak in South-east Asia, after Indonesia.

It has been tallying just 5,000 to 6,000 infections a day in recent weeks, from up to 15,000 cases a day in March and April.