The Olympics host city Tokyo, as well as Thailand and Malaysia, announced a record number of COVID-19 infections on Saturday, mostly driven by the highly transmissible Delta variant of the disease.

Cases surged in Sydney as well, where police cordoned off the central business district to prevent a protest against a strict lockdown that will last until the end of August.

Police closed train stations, banned taxis from dropping passengers off downtown and deployed 1,000 officers to set up checkpoints and to disperse groups. The government of New South Wales reported 210 new infections in Sydney and surrounding areas from the Delta variant outbreak.

Tokyo's metropolitan government announced a record number of 4,058 infections in the past 24 hours, topping 4,000 for the first time. Olympics organisers reported 21 new COVID-19 cases related to the Games, bringing the total to 241 since July 1.

The record comes a day after Japan extended its state of emergency for Tokyo to the end of August, expanding it to three prefectures near Tokyo and the western prefecture of Osaka in light of the recent spike in infections.

Olympics organisers said on Saturday they had revoked accreditation of a Games-related person or people for leaving the athletes' village for sightseeing, a violation of measures imposed to hold the Olympics safely amid the pandemic.

The organisers did not disclose how many people had their accreditation revoked, if the person or people involved were athletes, or when the violation took place.

Malaysia, one of the hotspots of the disease, reported 17,786 coronavirus cases on Saturday, a record number of infections.

More than 100 people gathered in the centre of the capital Kuala Lumpur, expressing dissatisfaction with the government's handling of the pandemic and calling on Prime Minister Muhyiddin Yassin to quit.

Protesters carried black flags and held up placards that read "Kerajaan Gagal" (failed government) – a hashtag that has been popular on social media for months.

Thailand reported a daily record of 18,912 new coronavirus infections, bringing the country's total accumulated cases to 597,287. The country also reported 178 new deaths, also a daily record, taking total fatalities to 4,857.

The government said the Delta variant accounted for more than 60% of the cases in the country and 80% of the cases in Bangkok.

The Delta variant is not necessarily more lethal than other variants, but much more transmissible, Supakit Sirilak, the director-general of the Medical Science Department, told Reuters.

China is also battling an outbreak of the Delta variant in the eastern city of Nanjing, traced to airport cleaners who worked on a flight from Russia.

COVID-19 infections have increased by 80% over the past four weeks in most regions of the world, WHO director-general Tedros Adhanom Ghebreyesus said on Friday.

"Hard-won gains are in jeopardy or being lost, and health systems in many countries are being overwhelmed," Tedros told a news conference.

The U.S. Centers for Disease Control said the variant, first detected in India and now dominant across the globe, is as contagious as chickenpox and far more contagious than the common cold or flu. It can be passed on even by vaccinated people, and may cause more serious disease than earlier coronavirus strains.