Cyber-security experts have expressed surprise that journalists at the summit between US President Donald Trump and North Korean leader Kim Jong-Un in Singapore were given USB-powered fans.

Some warned reporters not to plug them in to their laptops, as USB devices can carry malware.

The fans were part of a gift bag including a branded water bottle and a local guidebook.

Temperatures reached 33C in Singapore during the meeting.

Dutch journalist Harald Doornbos tweeted a picture of the fan.

The tweet reads: “Handy. In the press kit for the #KimTrumpSummit, there is a mini USB fan – convenient to stay cool while writing. It is pretty hot here in Singapore, 33C or so. But it does not reach Dubai, king of the oven.”

But cyber-security expert Prof Alan Woodward, from Surrey University, said: “For years now, engineering people to plug in a USB stick you supplied has been a classic way of circumventing security measures to get your software on their machine.

“There’s an adage in cyber-security: if you give someone physical access to your computer, it’s no longer your computer. Use an unknown USB stick and you are doing just that.”

The gift packs were assembled by the Singapore state company which manages the island of Sentosa where the summit took place.

The gifts have no known link with North Korea. which has been blamed for a number of cyber-security incidents, including the release of the Wannacry ransomware that struck the NHS in 2017.

The state has always denied responsibility for the attack.