Stefan Löfven told reporters the number of people being treated in intensive care has doubled in the past week.
Anders Tegnell warned young people could die of COVID-19 if the strategy were attempted.
Over 5,200 of Sweden's nearly 6,000 COVID-19 deaths were reported to be among those aged 70 and above, according to its public health agency.
Russian health officials confirmed nearly 16,000 new virus cases between Sunday and Monday, the largest single-day increase recorded since the onset of the pandemic.
Weekly new cases in Sweden rose for six consecutive weeks since the week commencing August 31, according to the World Health Organization.
The head of Tesla is a high-profile critic of COVID-19 measures, and has called for lockdown restrictions to be lifted.
Sweden is currently "reporting community transmission" of the virus, according to the World Health Organization.
Ndella Jack was shot 19 times as she lay in bed by assassins who had been targeting her husband who she had married just 12 days earlier.
Health officials are discussing the possibility of additional regulations in Stockholm, Sweden's capital city, in response to a recent uptick in COVID-19 cases.
Norway's state epidemiologist questioned the idea put forward by his Swedish counterpart Anders Tegnell.
Tegnell also said "of course something went wrong" with Sweden's approach, as over 5,800 people died of COVID-19.
Johan Carlson said keeping messages clear and consistent and getting the public to take personal responsibility helped limit spread of the virus.
A journalist made secret recordings of telephone conversations with jailed inventor Peter Madsen which are now set to be broadcast.
Emails previously showed Johan Giesecke and state epidemiologist Anders Tegnell discussing herd immunity at the start of the pandemic.
Approximately 3,700 residents received false positive results from the tests, according to the country's Public Health Agency.
Nodding to the concept of folkvett, or the common sense of the people as a collective, Sweden instead provided citizens with guidance on how to behave.
Sweden has seen a recent increase in weekly new cases starting from early August, according to the World Health Organization.
"I believe thousands are already infected in Sweden... it will all come to an end when so many have been infected and become therefore immune that the virus has nowhere else to go," one email read.
The percentage of people in Stockholm who had antibodies against the coronavirus was thought to be around 15 percent in May.
While Sweden's GDP fell in the second quarter, the country is not in a recession.
The lack of mandates relating to face mask use is at odds with much of Europe.
Sweden's seven-day rolling average of daily new deaths has been mostly declining since around mid-April.
The seven-day rolling average of daily new deaths in Sweden has also been declining for months.
Co-author Dr. Peter Kasson of the University of Virginia School of Medicine said: "The key finding is that individual actions matter."
A classic book about America's middle class returns just in time; Mitch McConnell faces a dilemma; and a COVID experiment in Sweden falters. So far.
The car company has issued its largest-ever recall, due to a seatbelt malfunction that can cause front seatbelts to wear and tear.
The Scandinavian country known for its light-touch approach to battling the pandemic reached 54,562 total coronavirus cases Wednesday. It is currently the second most-infected country per capita in the world.
Sweden, which has one of the highest per capita COVID-19 death rates in the world, is close to reaching 50,000 cases of the virus.