The global coronavirus death toll approached 700,000 Tuesday, as France and the Netherlands began tightening restrictions, and the Philippines placed millions of people back under lockdown.
The hunt for an effective treatment continued meanwhile, with the United States launching trials of an antibody treatment for COVID-19.
In France, the scientific committee advising the government over the coronavirus crisis, warned that the country could lose control of its spread "at any time".
Noting its increased circulation and that fewer people were respecting basic safety precautions, it warned: "The balance is fragile and we can change course at any time to a less controlled scenario like in Spain, for example."
Paris, Toulouse and other cities announced that the wearing of masks would be compulsory in particularly busy streets and squares. People are already obliged to wear them inside most private businesses and all public buildings.
In the Netherlands, the same measure will be applied in Rotterdam and the famous red-light district of Amsterdam from Wednesday.
And Ireland postponed the reopening of pubs and other nightspots on the advice of scientists, concerned about rising infections.
French hotel chain Accor meanwhile announced a cost-cutting plan that included 1,000 job losses Tuesday, a day after it blamed the pandemic for net losses of 1.5 billion euros for the first half of the year.
And the online travel agency Booking.com announced Tuesday it would cut up to a quarter of its 17,500 staff worldwide, its Amsterdam headquarters among the sites affected.
- Philippines resumes lockdown -
Millions of people in the Philippines were ordered to stay home Tuesday in a bid to contain the rising rate of infections, and relieve pressure on overwhelmed hospitals.
More than 27 million people on the main island of Luzon, including the capital Manila, went back into a partial lockdown.
People have been told to stay home unless going out to buy essential goods, for exercise or for work, after the number of recorded infections surged past 100,000.
But with only 24 hours' notice of the shutdown, many people were stranded in Manila, unable to get back to their hometowns after public transport and domestic flights were halted.
More than 18 million people worldwide have been infected with the virus since it first emerged in China late last year.
Far from slowing down, the latest figures show that the rate of infection is accelerating.
Brazil is driving a surge in Latin America and the Caribbean, where infections passed five million on Monday.
South America's largest country has recorded more than 2.75 million cases, and nearly 95,000 deaths, nearly half the region's 203,800 deaths.
Only the United States has been worse affected.
- US announces clinical trials -
The world's hope of ending the current cycle of outbreaks and lockdowns rests on finding a treatment.
The United States announced Tuesday it had begun late-stage clinical trials into a drug they hope will be an antibody against the coronavirus.
The Phase 3 trial will initially enrol some 300 volunteers around the world who have been hospitalised with mild to moderate COVID-19 with fewer than 13 days of symptoms.
On Monday, Russia said it aimed to launch mass production of one in September and turn out "several million" doses per month by next year.
In response, the World Health Organization on Tuesday urged Russia to follow the established guidelines for producing safe and effective vaccines.
Just a day earlier, the agency's chief Tedros Adhanom Ghebreyesus called on countries to focus on basic suppression measures, such as contact tracing, maintaining physical distance and wearing a mask.
"There's no silver bullet at the moment -- and there might never be," he warned.
- 'Extraordinarily widespread' -
As the number of virus deaths in the United States passed 155,000, President Donald Trump lashed out at his coronavirus response coordinator Deborah Birx after she warned the virus was "extraordinarily widespread" in the country where more than 4.7 million infections have been recorded.
Trump -- angered by what he sees as overly pessimistic media coverage of his handling of the epidemic -- accused her of giving into pressure to sound negative about the new surge.
"Deborah took the bait & hit us. Pathetic!" Trump wrote on Twitter Monday.
Despite rising infection numbers in Europe, some countries are pushing ahead with plans to reopen schools and finding ways to keep their battered tourism sectors functioning.
- Angry Nadal withdraws from US Open -Fears over the virus led defending champion Rafael Nadal to announce on Tuesday that he will not play the US Open which is due to start in New York on August 31.
"The situation is very complicated worldwide, the COVID-19 cases are increasing, it looks like we still don't have control of it." Nadal said on Twitter.
"This is a decision I never wanted to take... for the time being I rather not travel."
Women's world number one Ashleigh Barty withdrew from the tournament last week citing "significant risks" from COVID-19,