BEIJING — After the heavy losses of Chinese shares recently, executives, board members and controlling shareholders of more than 20 listed companies have announced their plans to increase shareholding of their firms in an effort to curb the losing streak.

Nine listed companies on the Shanghai Stock Exchange, including environmental protection firm Beijing GeoEnviron Engineering & Technology and 14 listed enterprises on the tech-heavy Shenzhen Stock Exchange made the announcement over the weekend, according to filings to two exchanges, showing executives and board members’ confidence in their companies.

Share financing from brokerages and other sources helped propel the Shanghai Composite Index to double within a year by June 12, but the market has been experiencing a slump over the past few weeks, with the index losing more than 28 percent from its peak on June 12 by July 3.

Many long-term investors and analysts said the market correction has created good investment opportunities.

“A raft of supportive monetary measures has been adopted and China’s economic growth has stabilized, so blue-chip companies and shares related to the Internet and state-owned enterprise reform enjoy sunny prospects,” said Shi Bo of South China Fund, a major equity fund management firm.

Twenty-five Chinese publicly offered funds reported confidence in maintaining a stable and healthy development of the stock market on July 4. Board chairmen and presidents of the funds said they will offer more products to buyers and promise they will vigorously purchase their own products and hold them for at least a year.