A group of start-ups led by a Hong Kong-based company Klook and backed by investors such as Japan’s SoftBank are expanding internationally in the $120bn travel activities industry, the fastest growing segment in the tourism sector.

The companies, which offer services ranging from amusement park tickets to cooking classes and walking tours, are targeting millennials, particularly in the rapidly expanding Asian travel market, forcing traditional travel agencies to invest more heavily in the sector.

“Asian inter-regional demand itself is as sizeable as the US or Europe, then you add on the growth,” said Eric Gnock Fah, co-founder of Klook, which claims to have raised the most capital of any tours and activities company globally. “In five years' time I think Asia as a whole will be bigger than the US and Europe. That’s why I think investors in general are optimistic about this sector.”