The World Health Organization (WHO) on Tuesday called for regulation of electronic cigarettes as well as bans on indoor use, advertising and sales to minors.

In a long-awaited report that will be debated by member states at a meeting in October in Moscow, the United Nations health agency also voiced concern at the concentration of the $3 billion US market in the hands of transnational tobacco companies.

The WHO declared war on "Big Tobacco" a decade ago, clinching the WHO Framework Convention on Tobacco Control, the world's first public health treaty that has been ratified by 179 states since entering into force in 2005.

NY Electronic Cigarettes

The World Health Organization is seeking a ban on indoor use of e-cigarettes, their advertising and sales to minors. (Frank Franklin II/Associated Press)

Prior to Tuesday's report it had indicated it would favour applying similar restrictions to all nicotine-containing products including smokeless ones.

The WHO urged a range of "regulatory options", including prohibiting e-cigarette makers from making health claims — such as that they help people quit smoking — until they provide "convincing supporting scientific evidence and obtain regulatory approval".

E-cigarettes should be regulated to minimize "content and emissions of toxicants", and those solutions with fruit, candy-like and alcohol-drinks flavours should be banned, it said. Vending machines should be removed in almost all locations.

Scientists are divided on the risks and potential benefits of e-cigarettes, which are widely considered to be a lot less harmful than conventional cigarettes.

One group of researchers warned the WHO in May not to classify them as tobacco products, arguing that doing so would jeopardize a major opportunity to slash disease and deaths caused by smoking.

But opposing experts argued a month later that the WHO should hold firm to its plan for strict regulations.

A total of 178 countries are parties to the FCTC and are obliged to implement its measures, with the United States the one notable non-signatory.

Major tobacco companies including Imperial Tobacco, Altria Group, Philip Morris International and British American Tobacco are increasingly launching their own e-cigarette brands as sales of conventional products stall in Western markets.

A Wells Fargo analyst report in July projected that U.S. sales of e-cigarettes would outpace conventional ones by 2020.

Uptake of electronic cigarettes, which use battery-powered cartridges to produce a nicotine-laced inhalable vapour, has rocketed in the last two years and analysts estimate the industry had worldwide sales of some $3 billion US in 2013.

But the devices are controversial. Because they are so new there is a lack of long-term scientific evidence to support their safety and some fear they could be "gateway" products to nicotine addiction and tobacco smoking.

A study by U.S. researchers published on Monday found they may be more tempting to non-smoking youths than conventional cigarettes.

Also on Monday, the American Heart Association's first policy statement on electronic cigarettes backed them as a last resort to help smokers quit.