The Philippines has announced a ban on the use and sale of e-cigarettes, a sudden and unexpected decision that seems to come as the result of an off-the-cuff comment made by the country’s authoritarian president Rodrigo Duterte.

A statement from the head of the Philippine police said that on “the order of the president… all police units nationwide to enforce the ban on use of vapes; ensure that all violators will be arrested”.

It comes after a 16-year-old Philippine girl was diagnosed with a “vape-associated lung injury” after using e-cigarettes for six months, prompting the Department of Health to raise concerns.

Doctors said the case is likely to be the first reported in Asia of the mystery lung illness that has killed almost 40 people in the US and sparked fears among regulatory bodies around the world. The girl, whose symptoms included sudden shortness of breath, was discharged after being treated.

Mr Duterte was asked about the vaping case during a televised late-night question-and-answer session on Tuesday.

“I will ban it,” he declared. “The use and importation. You know why? Because it is toxic and government has the power to issue measures to protect public health and public interest.”

The outspoken president was himself a heavy smoker until he was diagnosed as suffering from Buerger’s disease, which can cause blockages in the blood vessels. Since quitting himself, he has also banned the smoking of cigarettes in public.

Mr Duterte said e-cigarettes contain “nicotine and other chemicals that we do not know”, and that its users will “contaminate people”.

“This vaping, they say it is electronic. Don't give me that s**t. Better stop it, I will order your arrest if you do it in a room... That is like smoking,” he said.

The government released no formal order putting a ban in place. Mr Duterte’s finance minister Carlos Dominguez - who only last month ruled out a ban and suggested higher taxation would be a more effective measure - reportedly messaged MPs after the news conference asking them to start drawing up legislation immediately.

Initially marketed as a powerful tool to assist people in giving up smoking tobacco, e-cigarettes work by heating flavoured liquid to produce a vapour without most of the estimated 7,000 harmful chemicals present in traditional cigarettes.

E-cigarettes contain some of these chemicals, but at much lower levels. Public Health England says that while vaping “isn’t completely risk free… there is no situation where it would be better for your health to continue smoking rather than switching completely to vaping”.

And the UK body says an evidence review “found that to date, there have been no identified health risks of passive vaping to the health of bystanders”.

Nonetheless, critics say the widespread availability of flavoured e-cigarettes makes them more attractive to children, potentially leading to nicotine addiction among young people.

The US deaths have led a number of states to enforce or consider bans. The Centers for Disease Control and Prevention (CDC) has yet to identify any one product or chemical responsible for causing lung problems, but say it is possible unknown chemicals in black market e-cigarettes could be to blame.

Across the world, around 30 countries including Brazil and Singapore have banned vaping.

India became the largest to do so in September, in part citing the US deaths as a reason. Finance minister Nirmala Sitharaman said at the time that young people were “probably getting into the habit... as it seems cool”, while the health ministry said e-cigarette use across the developing world was reaching “epidemic proportions”.

Users in the Philippines were caught off guard by the sudden ban, which was confirmed by police less than 24 hours after Mr Duterte’s news conference, and the lack of a formal notice has left everyone in the dark over the potential penalties for being caught.