BANGKOK (AFP, The Nation/Asia News Network) - At least 16 Malaysian tourists were killed and eight others injured after their chartered bus crashed into another vehicle before hitting a power pole and crashing down a ravine in Chiang Mai on Sunday (Dec 20), police said.

Investigators said the accident happened around midday in Doi Saket district 30km from the northern city of Chiang Mai.

The bus was taking 21 Malaysian tourists to Chiang Mai when it hit a Toyota pickup in Mae Khachan district and the driver, Somporn Bualuang, accelerated to get away from the pickup.

The bus then hit a car before going off the road, police said.

Multiple images posted online by local news outlets showed a horrific scene as rescuers battled to reach those trapped inside the smashed bus, which had come to rest in thick foliage with its roof caved in.

Some of those still inside had suffered horrific injuries. In one picture seven pieces of white sheeting had been draped to cover either bodies or body parts. The bus driver and his helper were also among the injured.

Deadly road accidents are common in Thailand.

In a 2015 study on global road safety the World Health Organization found Thailand had the world's second most dangerous roads with 36.2 fatalities per 100,000 people.

The WTO said the number of official reported road deaths a year in Thailand for 2012, the latest year figures are available for, was 14,059.

But they added that their modelling suggested the true figure is actually closer to 24,000 dead a year.

Tourism is a mainstay of Thailand's otherwise fragile economy, accounting for around 10 per cent of GDP, and the December to February period is peak season.

The Chinese travel to Thailand in greater numbers than any other nationality.