(Yicai Global) Sept. 20 -- Some 21 cities in China have a population density of more than 1,000 people per square kilometer with Shenzhen being the most crowded city.

Shenzhen, a first-tier city in the southern Guangdong province, has more than 7,170 residents per sq km amid accelerating urbanization, according to public data. The technology hub has a total area of 2,465 sq km. 

Dongguan, a manufacturing hub close to Shenzhen, ranks second with a population density of nearly 4,260 people per sq km. Shanghai, China's most populous city, ranks third with almost 3,930 people per sq km.

The southeastern coastal city of Xiamen in Fujian province is No. 4 with almost 3,110 residents per sq km. The four cities in the economically developed Guangdong province, Foshan, Guangzhou, Zhongshan, and Shantou, follow next in the top eight.

Xiamen is the smallest among China's first and second-tier cities in terms of area but the municipality has well-developed tourism and modern service industries, Ding Changfa, associate economics professor at Xiamen University, said to Yicai Global. Xiamen also attracts a large number of migrants and ranks 33rd in terms of economic output among Chinese cities, Ding added.

Cities with a lot of nature and hills appear less crowded. Evidently, Beijing is No. 17 on the list with around 1,330 people per sq km. The capital city would rank higher if only downtown areas were included. Moreover, Hangzhou, an emerging first-tier city that is also quite hilly, has a relatively low population density.

In central and western China, only four cities, namely Zhengzhou in Henan, Wuhan in Hubei, Chengdu in Sichuan, and Xi'an in Shanxi, have more than 1,000 people per sq km. These provincial capitals have experienced rapid economic growth in recent years.

Editors: Dou Shicong, Emmi Laine, Xiao Yi