THIS is the horrific moment four people were killed when a bus driver accused of being asleep at the wheel piled into four cars backed up on a motorway.

Footage of the crash in Yeongdong, South Korea, shows vehicles being shunted aside when the out-of-control bus careens into them.

5 The bus speeds down the highway appearing to be fully under control Credit: YouTube

5 But the driver fails to see a queue of traffic in front of him - and rips through the first car it hits Credit: YouTube

5 Due to the speed it was travelling, it then smashed through several more queuing cars Credit: YouTube

5 At least four people were killed and another 37 wounded in the crash Credit: YouTube

Four people were killed in the crash, while another 37 were wounded.

Police said they were investigating whether the driver had fallen asleep or was using a mobile phone at the time - accusations the driver denied, joongboo.com reported.

Video of the deadly smash was recorded from another vehicle travelling just yards ahead of the bus.

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It showed the coach travelling along an open road seemingly without any vehicles ahead of it.

But when it gets close to a tunnel - the vehicle containing the camera peels off to the right to bypass the queuing traffic.

Remarkably, the bus does not slow down at all - it ploughs straight into the back of the queue.

The first vehicle appears almost completely decimated, while a second, third, fourth and fifth are all hit to varying degrees.

5 The vehicles were queuing outside the entrance to a tunnel in South Korea Credit: YouTube

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