Hundreds of thousands of people in China were in lockdown on Friday as the country battled its worst Covid-19 outbreak in months, while Japan -- a week into the Olympics -- extended its state of emergency due to surging infections.

The average number of new daily cases globally jumped by 10 percent over the last week, according to an AFP tally, largely due to the highly contagious Delta variant, after slowing between late April and mid-June.

Face masks are reappearing in cities around the world as the Delta variant fuels a surge in coronavirus cases Face masks are reappearing in cities around the world as the Delta variant fuels a surge in coronavirus cases Photo: AFP / Kena Betancur

While the Asia-Pacific region has been hard-hit -- with Vietnam and Japan recording a 61 percent jump in daily cases -- Western countries are also facing surges, with the US and Canada seeing 57 percent more infections.

The World Health Organization has warned that the Delta variant, first detected in India, could unleash more outbreaks in a high-risk zone stretching from Morocco to Pakistan where vaccination rates are low.

US President Joe Biden speaks about Covid-19 vaccinations at the White House U.S. President Joe Biden speaks about COVID-19 vaccinations at the White House. Photo: AFP / SAUL LOEB

In China, a cluster of infections in Nanjing city linked to airport workers who cleaned a plane from Russia earlier this month had reached Beijing and five provinces by Friday.

Hundreds of thousands of people have been locked down in Jiangsu province, of which Nanjing is the capital, while 41,000 came under stay-at-home orders in Beijing's Changping district.

Maps showing the change in the number of new cases in the prefectures of Japan, host country of the Olympic Games Maps showing the change in the number of new cases in the prefectures of Japan, host country of the Olympic Games Photo: AFP / Cléa PÉCULIER

The Philippines, which has closed its airport to most international travel for months, will send more than 13 million people in the national capital region back into lockdown next week because of a Delta-linked increase, the government said Friday.

In Israel, where this woman is being tested for Covid-19, the government has authorized booster shots for those over the age of 60 In Israel, where this woman is being tested for Covid-19, the government has authorized booster shots for those over the age of 60 Photo: AFP / MENAHEM KAHANA

And Japan extended a virus state of emergency in Tokyo and expanded the measure to four more regions after new cases topped 10,000 for the first time on Thursday.

Japan's case figures remain small compared to many places, with 3,300 new infections reported in Tokyo on Friday, but experts say the medical system is already at risk of being overwhelmed with only around a quarter of the population fully vaccinated.

The record cases come as Tokyo hosts the Olympics, where organisers on Friday reported 27 new cases related to the event -- the highest daily figure yet.

The surge in the United States has left many vaccinated people angry at those who have so far opted against a Covid-19 shot The surge in the United States has left many vaccinated people angry at those who have so far opted against a Covid-19 shot Photo: AFP / Kena Betancur

Australia said it would not reopen borders and end lockdowns until vaccination rates reach 80 percent.

US President Joe Biden says unvaccinated Americans are "sowing confusion" after being asked about potential uncertainty regarding the recent mask mandate. People fully vaccinated against Covid-19 in high-risk parts of the United States have been advised t US President Joe Biden says unvaccinated Americans are "sowing confusion" after being asked about potential uncertainty regarding the recent mask mandate. People fully vaccinated against Covid-19 in high-risk parts of the United States have been advised to resume wearing masks, a major reversal in guidance that underscored the country's struggle to suppress the Delta variant. Photo: DC POOL

In Germany, the government tightened restrictions on unvaccinated people entering the country, "regardless of whether they come by plane, car or train", Health Minister Jens Spahn said.

Governments of other wealthy countries have amplified efforts to get more of their populations to accept jabs.

Bolstering their case, new research shows that relaxing anti-virus measures before an entire population is vaccinated greatly enhances the risk of more resistant variants evolving.

At a time when nearly 60 percent of Europeans have received at least one vaccine dose, the authors said their study showed the need to maintain non-vaccination measures until everyone is fully jabbed.

"Delta is a warning: it's a warning that the virus is evolving but it is also a call to action that we need to move now before more dangerous variants emerge," the WHO's emergencies director Michael Ryan said.

More than four billion doses of vaccines have now been administered across the globe, according to AFP data.

High-income countries gave out an average of 97 shots per 100 inhabitants compared with just 1.6 in low-income nations.

Kenya, where only 1.7 million shots have been given to the population of 52 million, on Friday extended a nighttime curfew and banned public gatherings after a surge in Delta cases.

Health Minister Mutahi Kagwe said hospitals were becoming overwhelmed.

"If you fall sick today, you will not get a hospital bed," Kagwe said. "I am not scaring you, I am telling you the reality."

To help fill the vaccine gap, rich countries are stepping up donations to the less wealthy.

The US sent three million Moderna doses to Uzbekistan and one million doeses to Tunisia on Friday, following a delivery of 1.5 million Moderna jabs to neighbouring Tajikistan earlier this week.