China's southern boomtown of Shenzhen has added e-cigarettes to its smoking control list, further tightening the smoking ban in public places, according to a regulation passed Wednesday.

In China, smoking is banned in all indoor public places, workplaces and public transport. However, controversies exist on whether e-cigarettes shold fall into the smoking control category.

According to the new regulation, smoking e-cigarettes will be banned in Shenzhen's public places including bus platforms and waiting areas in public institutions.

The move follows other Chinese cities including Hong Kong, Macao, Hangzhou and Nanning, which have put in place similar e-cigarette bans.

E-cigarettes use battery-powered cartridges to produce a flavored vapor that often contains nicotine.

Young people make up the major demographic of e-cigarette smokers, according to a report released in May by the Chinese Center for Disease Control and Prevention. The e-cigarette usage rate has increased from 2015 to 2018, the report said.

So far, 42 countries and regions around the world have banned or restricted using e-cigarettes in public places.

China has set a target to reduce the smoking rate among people aged 15 and above to 20 percent by 2030 from the current 26.6 percent, according to the "Healthy China 2030" blueprint issued in 2016.