The number of newly reported Covid-19 cases has dropped dramatically, the World Health Organisation said on Wednesday, urging the world to seize the opportunity to end the pandemic.

Newly reported cases of the disease, which has killed millions since being identified in late 2019, last week fell to the lowest level since March 2020, said WHO chief Tedros Adhanom Ghebreyesus.

"We have never been in a better position to end the pandemic," he told reporters. "We are not there yet, but the end is in sight."

But the world needed to step up to "seize this opportunity", he added. "If we don't take this opportunity now, we run the risk of more variants, more deaths, more disruption, and more uncertainty."

According to WHO's latest epidemiological report on Covid-19, the number of reported cases fell 28 percent to 3.1 million during the week ending September 11, following a 12 percent drop a week earlier.

But the agency has warned that the falling number of reported cases is deceptive, since many countries have cut back on testing and may not be detecting the less serious cases.

"The number of cases that are being reported to WHO we know are an underestimate," Maria Van Kerkhove, the WHO technical lead on Covid, told reporters.

"We feel that far more cases are actually circulating than are being reported to us," she said, cautioning that the virus "is circulating at a very intense level around the world at the present time".

Since the start of the pandemic, WHO has tallied more than 605 million cases, and some 6.4 million deaths, although both those numbers are also believed to be serious undercounts.

A WHO study published in May based on excess mortality seen in various countries during the pandemic estimated that up to 17 million people may have died from Covid in 2020 and 2021. (AFP)