Three British tourists have been killed when their 4x4 jeep crashed off a bridge in Iceland, officials have said.

One of those killed was a child, and four other people who were in the vehicle have been seriously injured.

The accident occurred at around 9.30am when the vehicle slammed through a railing while crossing a high single-lane bridge at Skeidararsandur, a vast sand plain in southern Iceland.

The car, reported to be a Toyota Land Cruiser car rental, fell at least six metres (19.6ft) onto the river bed below on its side.

Emergency crews attended the crash site, described as "horrifying" by tour guide Adolf Erlingsson, who was among the first on the scene with two police officers.

"The car was totally smashed up after flying off the bridge and plunging down there," he told Icelandic radio station Bylgjan.

"When I arrived four had been retrieved from the vehicle, one was dead and three still stuck in the car, two of them probably dead. It was just awful.

"The car seemed to have hit the ground many metres from where it stopped. We struggled getting everyone out."

Police said it remains unclear what caused the driver to lose control of the vehicle.

Mr Erlingsson said that he cannot understand how the accident happened and had not noticed any ice on the bridge.

He said he was transporting 19 tourists around south Iceland in his own vehicle.

The bridge over Nupsvotn was built in 1973 and is 420 metres in length.

It is expected to be replaced in the next few years for a shorter bridge of around 100 metres long, according to information from the Road Administration.

There have been some accidents on the bridge in recent years, with news site visir most recently reporting a car and van collision in July.