How to call a landline in China from abroad?

Dial 86 + Area Code (2-3 Digits) + Local Landline Number 

For example, to call a Beijing landline from abroad:

86-10-xxxxxxxx

How can I call a landline in another Chinese city from China?

Dial 0 + Area Code (2-3 Digits) + Local Landline Number 

For example, to call a Chongqing landline from Shanghai:

0-10-xxxxxxxx