The WHO had committed a “total misinterpretation” of Swedish data, said Swedish state epidemiologist Anders Tegnell, whose country has made headlines for its high death toll after it opted not to introduce strict lockdowns.
“We have an increase in cases because we have begun testing much more in Sweden the past week,” he said, adding that “all the other parameters” showed the number of serious cases was falling.
The WHO's European branch on Thursday said Sweden was among 11 countries seeing an “accelerated transmission” that “if left unchecked will push health systems to the brink once again”.
The other 10 countries on the list are mostly poorer nations in Eastern Europe and Central Asia, which is included in the WHO's European region.
Around 5,280 people have died in Sweden from Covid-19, the world's fifth highest death rate – many times higher than its Nordic neighbours, which all imposed much stricter measures to combat the pandemic.
“The number of admissions to intensive care is at a very low level and even deaths are starting to go down,” Tegnell said.
“We are now down to a level where there are not more people dying now than during the same weeks in previous years.”
According to Sweden's Public Health Agency, around 10 coronavirus patients a day are being admitted to intensive care units, compared with 45-50 a day in April.
WHO's European branch acknowledged later that the Swedish government “has increased testing and this is reflected in the number of new cases reported since early June”.
An e-mail sent to AFP added that “there are several very positive trends in Sweden”.
In the past month, Sweden has more than doubled its Covid-19 testing and only began offering mass testing to the public last week, a delay which has been highly criticised.
WHO's European branch also added that the number of new cases “remains relatively high in Sweden” and the country “is still faced with community transmission”.
The e-mail did not say if Sweden would be removed from the list of 11 countries.