The number of swine flu deaths in Europe has doubled almost every two weeks since the middle of October with 169 people dying of the virus in the past week.
The Stockholm-based European Centre for Disease Control and Prevention said 670 deaths have been reported in Europe from H1N1 flu since they began monitoring it in April and all 31 European Union and European free trade area (EFTA) countries now have cases of the virus.
"The numbers of deaths...has shown a steady increase -- almost doubling every fortnight over the last six weeks," it said in its daily update.
"While the most deaths have to date been in Western Europe there are increasing numbers of deaths being reported from central and eastern Europe."
Vaccination programs against H1N1 have started in many European countries in recent weeks to try to halt the spread of the virus, which was declared a pandemic by the World Health Organisation (WHO) in June.
But immunisation plans are facing mixed levels of uptake and opposition from anti-vaccine lobbyists, according to the European Society of Clinical Microbiology and Infectious Diseases (ESCMID). It said such opposition was putting "public health and lives" at risk.
"No one can afford to be complacent or sceptical about the benefits of the H1N1 vaccine," ESCMID's president Javier Garau said in a statement. "The serious consequences of skipping the flu jab must be considered...and physicians must make clear the safety and vital protection role the vaccine has to play."
The WHO said last week that governments across the world have administered more than 65 million H1N1 vaccine doses. Common side effects of the shots include swelling, redness or pain at the injection site, and sometimes fever or headache but the WHO ruled out any death links to the shots.
The ECDC reported "very high intensity" of flu-like illness in the past week in Italy, Norway and Sweden and said intensity was "high" in Bulgaria, Denmark, Germany, Iceland, Ireland, Lithuania, Luxembourg, Poland and Portugal. The rest of Europe had mainly "medium" intensity, it said.
The ESCMID said flu levels were "unusually high for this time of year," with H1N1 accounting for 99 percent of cases.
It said it feared "deliberate misinformation" about H1N1 shots was being spread by a growing anti-vaccination movement and warned that a low uptake could hamper efforts to control the pandemic and increase pressure on health systems across Europe.
Some people say they fear the new H1N1 vaccines have been rushed through medicine regulation processes and not tested widely enough. But regulators, health experts and the WHO say the shots are safe, effective and offer vital protection.
"No one should reject a safe and effective vaccine when we are dealing with an unpredictable virus capable of killing children and young adults in their prime," Garau said.