China Shenhua and GD Power Development Co said in announcements on Sunday that their shares will be suspended from trading effective Monday.
Their announcements were posted on the website of the Shanghai Stock Exchange.
China Shenhua, the country's largest coal miner, was told by its majority shareholder, Shenhua Group on Friday that the company will be involved in an "important event" that has not yet been confirmed, according to the company's announcement.
Shenhua's shares were suspended to protect the interests of investors and prevent abnormal price fluctuations, it noted.
GD Power also on Friday received a notice from its parent company, China Guodian Corp, one of the country's biggest coal-fired power generators, saying that it should suspend trading its shares.
Rumors have circulated about a merger of Shenhua Group and China Datang Corp, one of China's five biggest coal-fired generators.
But both companies have denied that any such merger was coming, according to a report by Chinese media outlet ifeng on Sunday.
China Datang, Shenhua Group and China General Nuclear Power Corp, the largest nuclear power operator, as well as a major rail operator and power producer, will be combined to create a power giant, Bloomberg reported in May.
China Guodian Corp and China Huadian, which is also a major coal-fired power generator, may merge with China National Nuclear Corp, the second-largest nuclear power operator in China, to form a new company, Bloomberg said.
However, the proposal to restructure the State-run power sector through a series of mergers has not been finalized and is subject to change, it added.
Prospective mergers at the group company level of State-owned enterprises administered by the central government are mainly concentrated in sectors including coal and power, heavy equipment manufacturing and steel, the National Development and Reform Commission told a press briefing on Friday, the Xinhua News Agency reported the same day.