Dozens of stranded tourists were rescued when flash floods surged through a park in northern Thailand.

Twenty-five visitors were exploring the Op Luang National Park when torrential rain caused a river to swell in Chiang Mai province on Monday afternoon.

More than 50 volunteers were dispatched as water levels rose rapidly, leaving the group, including children, trapped.

Footage shows officers setting up a zipline to help the tourists cross over the raging deluge. All tourists were rescued unharmed.

Park chief Chayanan Sakum said the Mae Tia Waterfall will be closed starting today until the water level recedes.

Authorities said Doi Inthanon National Park saw 76 millimetres (three inches) of rainfall today.

Park authorities have deployed rangers to high-risk areas to warn tourists to stay away from waterfalls due to safety concerns.