This is the dramatic moment a dust devil tornado ripped through a hospital construction site, leaving workers stunned as they watched.

Muhammad Asnawi and his colleagues witnessed the sudden vortex forming on the ground in Sarawak, Malaysia.

Footage shows the whirlwind starting as a subtle gust before growing into a larger funnel of swirling air, which eventually dissipated after a few minutes on July 29.

Muhammad and his friends kept their distance until the phenomenon faded away.

He said: 'This was the first time I have seen a tornado like this one. It was strong and I could feel it blowing me.'

Dust devil tornadoes are types of whirlwinds that form when the sun heats a patch of land, and the air above becomes warmer and rises quickly.

Cooler air then moves into the low-pressure gap left by the rising warm air. The new drafts of cooler air also heat up and rise and the cycle continues, picking up dust and debris and making the spiral visible.

They are not as dangerous as supercell tornadoes, which can cause severe damage.