GENEVA (AP) -- Cigarette packages should include images of sickness and suffering caused by tobacco, along with written warnings, the World Health Organization said Friday.

The U.N. agency urged governments to make people more aware of the health consequences of smoking. It said most countries still do not warn consumers of the risks on packages of cigarettes, cigars and other tobacco.

"Health warnings on tobacco packages are a simple, cheap and effective strategy that can vastly reduce tobacco use and save lives," said Dr. Ala Alwan, a senior WHO official. "Warnings that include images of the harm that tobacco causes are particularly effective at communicating risk and motivating behavioral changes, such as quitting or reducing tobacco consumption."

Tobacco is the leading cause of preventable death, killing more than 5 million people worldwide each year. WHO says it is the only legal consumer product that kills when used exactly as intended by the manufacturer.

Warning pictures on cigarette and other tobacco packs have helped smokers kick the habit and prevented others from becoming addicted, WHO said. It cited studies of such campaigns in Brazil, Canada, Singapore and Thailand, and said they revealed "remarkably consistent findings."

But only a tenth of the world's population lives in countries requiring warning pictures, WHO said. It said governments needed to address that shortcoming as ignorance still prevails on the dangers of smoking.

For example, a study in China showed that barely a third of smokers knew they were at higher risk of heart disease and only 17 percent knew that smoking causes strokes, the agency said. In Syria, just a fraction of university students knew that cardiovascular disease was a hazard of cigarette or water pipe smoking.

WHO has taken an increasingly strong stance against tobacco in recent years. It sponsored a 2003 treaty to control tobacco use and has urged a world ban on smoking in indoor workplaces and public buildings. It also has said it will not hire any prospective employees who smoke or use other tobacco products.

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