Four major coal companies are to raise the price of their coal ready for shipment at ports by 10 yuan ($1.5) per ton during June.

Shenhua Group Corp, China Coal Energy Group Co Ltd, Datong Coal Mine Group and Inner Mongolia Yitai Group Co Ltd revealed the move on Friday.

According to a report by Citibank China analysts Jack Shang and Claire Jie Yuan, the decision is part of the government's ongoing effort to limit national coal production, which could eventually result in as much as 20 percent added to the price by the end of the year.