LONDON -- The Taliban has claimed responsibility for an attack in Kabul Saturday. More than 100 people were killed and twice as many were injured when an attacker drove an ambulance packed with explosives into the heart of the city.

It's not hard to buy a used ambulance. CBS News posed as buyers and found one on eBay. But according to security experts like Chris Phillips, the resale of emergency vehicles is handing terrorists a lethal weapon.

"The terrorist threat is wider, it's more diverse," said Phillips. "One of those attacks will almost certainly be a vehicle bomb."

It's a threat that British security services flagged a decade ago when they were being used in Iraq. They're called Trojan vehicles, seemingly ordinary ambulances that are instead packed with explosives.

Afghan volunteers and policemen carry injured men on an ambulance at the scene of a car bomb exploded in front of the old Ministry of Interior building in Kabul on January 27, 2018. AFP PHOTO / WAKIL KOHSAR (Photo credit should read WAKIL KOHSAR/AFP/Getty Images) Wakil Kohsar / AFP/Getty Images

"You're not going to know that the ambulance coming towards you is a real one or a fake one," Phillips said.

He also said the fear is that tactic will be imported here as terror attacks by Islamic militants grow.

"There needs to be some kind of legislation to stop the use of these vehicles or we're going to have a major problem with this."

We found plenty of examples on eBay. A police car with original equipment in the truck, an ambulance with full emergency markings -- most run for just a few thousand dollars.

"Anyone can turn up, they can pay cash for the vehicles and within hours those vehicles can be in the hands of a terrorist cell," said Lord Carlile of Berriew, who led calls to outlaw the resale of emergency vehicles.

Ambulances can be found for sale online CBS News

But there are still no clear regulations governing the resale of ambulances. Lord Carlile pointed out last year's Ariana Grande concert where 60 ambulances raced to the scene, is exactly the scenario where a Trojan vehicle could exploit the chaos.

"That is the sort of place where the risk of one of these vehicles entering the cordoned off zone in the minutes immediately after the explosion takes place is a very high risk," he said.

We contacted the home office, Britain's counter-terrorism authority repeatedly, and we were told they're looking into it. EBay said fully operational emergency vehicles are not allowed on their website, and they're reviewing the ads we pointed out.