The rankings were changed after the UN used new criteria to give a more accurate picture of the rapid urbanisation driving the growth of megacities

In just seven years, Jakarta, Indonesia, took a giant leap from 33rd biggest city in the world to surpass Tokyo at the top of the list as it has grown to 42 million residents.

Nine of the top 10 mega-cities are in Asia, with Bangladesh's Dhaka projected to be the world's largest city by 2050.