In Australia around a million in Sydney neighbourhoods were ordered to stay home for at least a week.
Australia and Israel, which had been successful in fending off Covid-19, reimposed restrictions on Friday as cases surged of the highly contagious Delta variant which also threatened Africa with a brutal third wave.
The centre of Australia's largest city Sydney entered lockdown, a shock for a population that had returned to relative normality after months of recording very few local cases, while vaccination success story Israel reimposed indoor mask-wearing less than two weeks after it lifted the measure.
And in Fiji, another country that saw early successes against the virus, health authorities admitted for the first time that Covid transmission is widespread in the community.
While vaccination campaigns have helped bring down infections in numerous -- mostly wealthy -- countries, the rise of the Delta variant which was first found in India has led to fears of new waves of a virus that has already killed nearly 3.9 million people.
In Australia, which has been one of the most successful nations in containing the coronavirus after shutting its borders, around a million people in four eastern and central Sydney neighbourhoods were ordered to stay home for at least a week.
Sixty-five infections have been reported in a flare-up linked to a limousine driver infected about two weeks ago when he transported an international flight crew from Sydney airport to a quarantine hotel.
The premier of the state of New South Wales, Gladys Berejiklian, called it the "scariest period" since the pandemic began.
It was a dramatic development for a city that had returned to relative normality after months of recording very few local cases.
Bondi local Alana Trepper said "to be honest, I probably think that it should have happened a couple of days ago because there's been a pretty decent spread the last few days."
Israel puts masks back on
Israel, which has prided itself on having one of the world's most successful vaccination campaigns, has seen infections surge since dropping a requirement to wear masks in enclosed public places 10 days ago.
After four days of more than 100 new cases a day -- including 227 on Thursday -- the health ministry reversed the decision.
The head of Israel's pandemic response taskforce, Nachman Ash, said the rise was likely due to the Delta variant, adding that the increasing cases were not yet matched by a parallel rise in hospitalisations or deaths.
Fiji meanwhile recorded a surge of 300 new daily infections on Thursday, after going a full year without recording a single community case until April -- when the Delta variant arrived.
But with numbers doubling every nine days, the government's head of health protection, Aalisha Sahukhan, said "all the evidence is that there is widespread community transmission".
Russia is also battling rising Delta cases, reporting more than 20,000 cases on Thursday, the country's highest number since January.
'Brutal' third wave in Africa
And in Africa, which has so far been spared the worst of the pandemic, infections are surging at an alarming rate in at least 12 countries, with continental cases expected to hit a record peak in around three weeks.
Africa Centres for Disease Control and Prevention (Africa CDC) director John Nkengasong described the third wave hitting the continent as "extremely brutal" and "very devastating".
The Delta variant has been reported in 14 African countries, making up the bulk of new cases in the Democratic Republic of Congo and Uganda, according to the World Health Organization.
Unprecedented hospital admissions and fatalities have pushed health facilities to the brink, with Zambia's mortuaries "overwhelmed" by Covid deaths, the Africa CDC said.
According to the WHO, about one percent of the continent's population is fully vaccinated, the lowest ratio globally.
WHO Africa director Matshidiso Moeti said cases are "outpacing vaccinations".
"Africa urgently needs a million more vaccines. We need a sprint".