Governments should ban the use of electronic cigarettes in public places and outlaw tactics to lure young users, the World Health Organization said in a report released on Tuesday that calls for some of the toughest measures yet proposed for the increasingly popular devices.

It also expressed “grave concern” about the growing role of the powerful tobacco industry in the e-cigarette market, warning that the financially powerful companies could come to dominate the new business and use the current tolerance of the new products as a gateway to ensnaring a new generation of smokers at a time when the public health authorities seem to be winning the battle against tobacco.

The proposals by the organization, a United Nations agency, are only recommendations that might have little likelihood of being widely adopted. But health experts said they would serve as an important reference point for policy makers, both nationally and locally, as they try to navigate the complex balance of benefits and risks with very little science on which to base conclusions.

And the report seems likely to spur further intense lobbying by the tobacco and e-cigarette industries against more regulation.

Many health experts welcomed the recommendations, which they said would help guide policy makers around the world as they struggle to keep up with a multibillion-dollar industry.

But some experts said they worried that the proposals were so restrictive that they might undermine the potential benefits of e-cigarettes, which, because they use battery-powered heating units to vaporize a liquid nicotine solution rather than burn tobacco, might not expose users to as many hazards as conventional cigarettes. Some experts have even argued that e-cigarettes have the potential to drastically reduce rates of smoking, one of the biggest causes of preventable death worldwide, and so should not be overregulated.

“We’re disappointed,” said David Abrams, executive director of the Schroeder Institute for Tobacco Research and Policy Studies in Washington. “They are overregulating by equating e-cigarettes with regular cigarettes. We have to find a balance between protecting youth and helping smokers quit. This document doesn’t do that.”

Mr. Abrams was one of more than 50 public health experts who recently signed a letter calling on the World Health Organization to moderate its approach to e-cigarettes by calling for lighter regulation than applies to cigarettes.

But in its report, the organization said that because there were still too many uncertainties surrounding e-cigarettes, which have been on the market for less than a decade, their use indoors should be banned “until exhaled vapor is proven to be not harmful to bystanders.”

The report also called for regulation to ensure the products contain a standard dose of nicotine, as the drug content now varies widely among manufacturers. And to stop children from picking up the habit, it said that e-cigarette sales to minors should be banned and that fruity, candy-type flavorings should be prohibited.

The 13-page report, which summarizes the growing body of evidence on the health impact of electronic cigarettes, was prepared by the World Health Organization for the United Nations Framework Convention on Tobacco Control, to be held in mid-October in Moscow. The organization has no power to enforce its recommendations, but delegates to the meeting could, in theory, endorse the measures for inclusion in the treaty or call for yet more studies before taking further action.

The proposals come from the same organization that successfully pushed for the United Nations tobacco treaty, adopted in 2003, that is intended to reduce illnesses and deaths caused by tobacco. The signatory countries promise to eliminate or limit tobacco advertising, to raise cigarette taxes and to take steps to end smoking in public places.

Under the administration of former President George W. Bush, the United States signed the treaty in 2004. But Mr. Bush never sent it to the Senate for ratification and President Obama has yet to do so. That leaves the United States, along with Argentina, Cuba, Haiti, Morocco, Mozambique and Switzerland, as the only countries among the treaty’s roughly 180 signatories not to have ratified it.

The rapid growth of the market for e-cigarettes has left national regulatory systems and health policy experts struggling to keep up, as old notions about the dangers of tobacco and smoking are posed in a new light. The health body said that there were now 466 brands of e-cigarettes globally, in a market valued last year at $3 billion. The market research firm Euromonitor forecasts sales will swell by a factor of 17 by 2030.

Anecdotal evidence suggests that e-cigarettes may hold promise as smoking cessation aids. But the World Health Organization report noted that there was scant evidence for their effectiveness in helping smokers give up the habit.

“Vapers,” as e-cigarette aficionados are known, have become a potent lobby on behalf of the products. Their support helped the tobacco industry defeat a European Commission proposal that the devices be regulated in Europe as medicines. In February, the European Parliament voted to adopt a set of rules that include a ban on advertising. The tobacco industry is lobbying to water down the measures before they are to go into effect in 2016.

In the United States, the Food and Drug Administration proposed in April extending its regulation of tobacco products to include e-cigarettes, with a ban on their sale to people under 18. The proposal remains under consideration.

The number of young Americans who have tried electronic cigarettes but never used conventional tobacco tripled in 2013 from 2011, to more than 250,000, according to a report on Monday from the Centers for Disease Control and Prevention in Atlanta. Youth smoking rates in the United States dropped by half from 1997 to 2011, according to federal data, but the pace of the decline has slowed in recent years. Many health advocates worry that e-cigarettes may lead teenagers to use conventional cigarettes instead of serving as an alternative to them.

The World Health Organization’s proposal to limit smoking in public places goes substantially further than the European Union’s rules, which leave the decision about whether to restrict e-cigarette use to the 28 European Union member states. Some among them, including Britain and France, have said they were considering such measures.

The rules being considered by the F.D.A. in the United States do not address where e-cigarettes can be smoked. That policy decision, at least for now, is made mostly at the local level, with a number of states and cities banning the use of e-cigarettes in public places. Until recently, the American government had not even asserted its authority over e-cigarettes, leaving the entire industry virtually unregulated.

The World Health Organization report worries that Big Tobacco is becoming “increasingly aggressive in the battle for the fast-growing e-cigarette market.” It said that while the current crop of independent e-cigarette companies had “no interest in perpetuating tobacco use, the tobacco industry involved in the production and sale of electronic nicotine delivery systems certainly is.”

Philip Morris International, which this year bought one of Britain’s biggest e-cigarette makers, Nicocigs, said the World Health Organization was unfairly singling out tobacco companies, which a spokesman argued were well placed to create the best e-cigarette products.

“The W.H.O. has once again called for de facto exclusion of tobacco companies in the democratic process,” said the spokesman, Tommaso Di Giovanni. “This view ignores the fact that product innovation to develop and assess truly reduced risk alternatives to combustible cigarettes can play an important role for public health.”

Companies like Philip Morris, Mr. Di Giovanni argued, “are not only driving this innovation, but have the necessary knowledge and resources to contribute to achieving that goal.”