The drug-resistant strains are also spreading fast across the continent, officials warned. They were found in 17 European countries in 2010, seven more than in the previous year.

Gonorrhoea was the second most common sexually transmitted infection (STI) in Europe in 2010, with more than 32,000 infections, data from the Stockholm-based European Centre for Disease Prevention and Control (ECDC) showed.

Even though chlamydia was the most frequently reported STI, with more than 345,000 cases, the ECDC's director singled out gonorrhoea as presenting a "critical situation".

Marc Sprenger said the increase in cases of superbug strains meant there was a risk gonorrhoea may become an untreatable disease in the near future.

The proportion of gonorrhoea cases with resistance to the antibiotic recommended to treat the disease, cefixime, rose from 4 percent in 2009 to 9 percent in 2010.

The ECDC report follows a warning from the World Health Organisation that virtually untreatable forms of drug-resistant gonorrhoea were spreading around the world.

Gonorrhoea is a bacterial infection which, if left untreated, can lead to pelvic inflammatory disease, ectopic pregnancies, stillbirths, severe eye infections in babies, and infertility in men and women.

VIGILANT

It is one of the most common sexually transmitted diseases in the world and is most prevalent in South and Southeast Asia and sub-Saharan Africa.

In the United States alone, the number of cases is estimated at about 700,000 a year, according to the Centers for Disease Control and Prevention (CDC).

The emergence of drug-resistant gonorrhoea is caused by unregulated access to and overuse of antibiotics, which help fuel genetic mutations within the bacteria.

"Public health experts and clinicians need to be aware of the current critical situation and should be vigilant for treatment failures," Sprenger said in a statement.

Experts say the best way to reduce the risk of even greater resistance developing - beyond the urgent need to develop new drugs - is to rapidly and accurately diagnose the disease and then treat it with combinations of two or more types of antibiotics at the same time.

This technique is used in the treatment of some other infections like tuberculosis in an attempt to make it more difficult for the bacteria to learn how to overcome the drugs.

The ECDC's sexually transmitted infections report covered data and trends on five STIs - syphilis, congenital syphilis, gonorrhoea, chlamydia and lymphogranuloma venereum (LGV) - in the EU and European Economic Area from 1990 to 2010.

It found diverging trends in sexually transmitted diseases across Europe, with a rapidly increasing trend for chlamydia and slightly decreasing trends for gonorrhoea and syphilis.

Genital chlamydia infections are caused by Chlamydia trachomatis bacteria which can irreversibly damage a woman's reproductive organs.

Although the disease is easily treated with antibiotics, infections can remain undiagnosed because many patients - 70 percent of women and 50 percent of men - have no symptoms and so are unaware they are carrying and passing on the infection.