Electronic cigarettes do not help smokers to quit as marketers claim and may be toxic, the World Health Organization said Friday.

The devices resemble a real cigarette, but consist of a stainless steel tube with a chamber that holds liquid nicotine. The E-cigarettes have been marketed as a healthier alternative to tobacco, and since they do not need to be lit, some people are using them to evade smoking bans in public places, the UN health agency said.

The device is powered by a rechargeable battery and produces a heated mist of nicotine that is absorbed in the lungs.

Electronic cigarettes were first developed in China in 2004, and are now sold there as well as in Brazil, Canada, Finland, Israel, Lebanon, the Netherlands, Sweden, Turkey and the United Kingdom.

"The World Health Organization knows of absolutely no scientific evidence whatsoever that would confirm that the electronic cigarette is a safe and effective smoking cessation device," Douglas Bettcher, acting director of the WHO's Tobacco Free Initiative, told reporters.

"There are a number of chemical additives in the product which could be very toxic."

Some manufacturers have implied that WHO considers electronic cigarettes to be a legitimate form of nicotine replacement therapy, like nicotine gum, patches and lozenges.

"Manufacturers of this electronic cigarette around the world have included WHO's name or logo, for example, on their website, on package inserts or on advertisements," Bettcher said, without naming any company or manufacturer.

Dr. Ala Alwan, assistant director general of WHO's noncommunicable diseases and mental health branch, called on electronic cigarette marketers to immediately remove any suggestion that WHO considers it a smoking cessation aid from their websites and promotional materials.

Use of tobacco is the single largest cause of preventable deaths worldwide. It contributes to 5.4 million deaths from heart disease, stroke and other diseases annually, the agency said.