China has further tightened smoking restrictions - targeting schools and day care centres - as it extends a crackdown linked to its pledge to hold a smoke-free Olympics.

Last month, Beijing formally pledged to restrict smoking in most public venues in the city, including government offices and public transport, beginning on May 1.

In a separate move reported on Wednesday, China ordered primary schools, secondary schools and day care centres across the country to prohibit even designated smoking zones, an effort to promote 'non-smoking campuses' ahead of the Games.

"Smoking rooms and zones are banned within teaching regions effective immediately," the Beijing News cited an order by the Health Ministry as saying.

The Health Ministry also approved an order on Tuesday requiring all schools to incorporate into their curricula programs that inform students about the harmful effects of smoking and second-hand smoke.

"All teaching and administrative staff are vigorously encouraged to quit smoking," the order added.

In October, China banned smoking in taxis, and last month urged government employees to refrain from accepting or offering cigarettes on social occasions, in a move to curb social smoking.

But smoking at official functions and in social settings is an entrenched part of Chinese life. Notably, its recent campaigns have so far refrained from outright smoking bans at restaurants, bars and clubs.

China is the world's largest cigarette producer, and Chinese are the world's most enthusiastic smokers, with a growing market of about 320 million smokers making it a magnet for multinationals and a focus of international health concern.

The newspaper added that a poll of student smokers under the age of 15 showed that 22.4 percent of young smokers were male and 3.9 percent female.