With its booming population as well as thriving economy, China dominates Forbes Magazine's list of top 12 fastest growing cities in the world. However, the city that topped the list was Karachi in Pakistan.

A city is considered a megacity when it has a population of more than 10 million people. Given this definition, the top 7 megacities are found in Asia and the highest ranking western megacity is New York, ranked at eighth place.

The top 7 is make up of Tokyo-Yokohama in Japan, Jakarta in Indonesia, Seoul-Incheon in South Korea, Delhi in India, Shanghai in China and Metro Manila in the Philippines.

Outside New York, other western cities on the megacity lists are Moscow at 15th place, Los Angeles at 17th and Paris at 28th. In 1990, New York was on second place and LA on 8th.

In coming up with a list of fastest growing cities, Forbes used the updated population data released in March by Demographia.

Karachi was number one on the list because within the 10-year period 2000 to 2010, it logged an 80 per cent growth rate to 20.88 million headcount.

Karachi is the capital city of Pakistan, serving as the hubs for banking, industry, trade and is the headquarters of the country's largest companies engaged in textile, shipping, automotive, entertainment, arts, fashion, advertising, publishing, software and medical research sectors.

The other fast growing cities on the list are:

1. Shenzhen, China - 12.51 million, 56.1 per cent growth

2. Lagos, Nigeria - 12.09 million, 48.2 per cent

3. Beijing, China - 18.24 million; 47.6 per cent

4. Bangkok, Thailand - 14.54 million; 45.2 per cent

5. Dhaka, Bangladesh - 14.34 million; 45.2 per cent (tied with Bangkok)

6. Guangzhou-Foshan, China - 17.69 million; 43 per cent

7. Shanghai, China - 21.77 million; 40.1 per cent

8. Delhi, India - 22.83 million; 39.2 per cent

9. Jakarta, Indonesia - 26.75 million; 34.6 per cent

10. Istanbul, Turkey - 12.92 million; 25.3 per cent.

Citing UN projections, Forbes said by 2025, the list of megacities would be made by mainly of lower-income cities in Africa and Central Asia. It said the likely additions to the list are Lima in Peru, Kinshasha in Congo and Tianjan in China.

By 2030, another eight cities would likely be included, namely: Chennai, Bangalore, Bogota, Ho Chi Minh City, Dongguan, Chengdu and Hyderabad, as their headcounts soars above 8 million.