Retailers are openly flouting the ban on tobacco sales near schools in Changsha, the capital of Hunan province in South-Central China, reveals research published online in the journal Tobacco Control.

Furthermore, marketing strategies targeting children are "pervasive," the study shows, prompting the authors to urge officials to take swift action to enforce the regulations.

Tobacco retail sales are prohibited within 100 metres of schools in many large cities in China, but it's not clear how well this zoning regulation is being enforced.

The researchers therefore audited activity (sales and outlet density) within 200 m of 36 schools and in 36 residential areas of the city of Changsha, in Hunan Province in South-Central China between December 2014 and January 2015.

On average, they found three retail outlets selling tobacco within 100 m of each of the schools and nearly seven within 100-200 m. Almost all the schools (98%) had at least one shop selling tobacco within a 100 m radius.

The density of retail outlets was similar near schools and in residential areas, but was significantly higher within a 100 m radius of a school than it was within a 200 m radius.

Around one in four stores displayed at least one external tobacco ad, although these were more common in residential areas than near schools.

Most (73%) outlets displayed tobacco products at the primary check-out counter and in 44% of stores these products were clearly visible from outside.

Marketing strategies targeting children were also "pervasive" the audit showed, with 83% of shops displaying tobacco products within 1 metre of the floor, while 60% displayed them within 30 cm of toys, confectionery, and gum.

These strategies were more common in stores near schools and in those within a 100 m radius of a school.

Only around one in five retail outlets selling tobacco had a 'no smoking' sign prominently displayed, and this was particularly true of shops near schools. And not many outlets displayed a 'no sales to minors' sign--also required by law.

Although retailers in China are required to have a licence to sell tobacco, fewer than half of those audited had one displayed in store.

In Changsha, the Tobacco Monopoly Bureau (TMB) is responsible for monitoring and enforcing the regulations, added to which national legislation bans the sale of tobacco products to anyone under the age of 18.

But write the researchers: "Our findings indicate that the TMB has failed to monitor and enforce these regulations. For example, at least 40% of tobacco retail stores located within 100 m of the front entrance of schools were issued a tobacco retail licence though tobacco retail sales are prohibited in this area."

They add: "Effective enforcement of such regulations is needed to protect youth. Additionally, point of sale tobacco displays and tobacco advertising are urgently needed in China."