China, the world's biggest consumer of tobacco, has insisted it will honour a pledge to ban smoking in public places by 2011 in accordance with an international treaty, state media said Tuesday.

The health ministry said it intended to implement a plan to prohibit smoking from next year in all indoor public places and offices, as well as on trains and buses, the Global Times reported.

Senior ministry official Yang Qing said the goal had been set in accordance with the World Health Organization's Framework Convention on Tobacco Control, which came into force in early 2005. China ratified it that same year.

The treaty calls for signatory nations to put in place "effective legislation" and other measures which provide for "protection from exposure to tobacco smoke" in indoor public places.

But one activist and an official at a government agency raised doubts that the rules could be implemented in a country where more than a quarter of the population smokes.

"Law enforcement is not in place, so regulations exist in name only," the Global Times quoted Yang Gonghuan, deputy director of the China Centre for Disease Control and Prevention, as saying.

Wu Yiqun, deputy director of the anti-smoking advocacy group Thinktank, said she believed the chances of a nationwide ban working were slim, the China Daily reported.

Numerous Chinese cities already have bans on smoking in public places, but enforcement remains weak.

About 350 million of China's 1.3 billion people smoke cigarettes, with the nation consuming up to one-third of the tobacco products sold annually worldwide, according to the Chinese Association on Tobacco Control.

Up to one million Chinese die every year from lung cancer or cardiovascular diseases directly linked to tobacco consumption, it said in a release last year.

In December last year, the WHO said only 17 countries had enforced bans on smoking in public places.