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Major shareholders of Chinese companies pledge not to sell shares during market slump

SINGAPORE (Reuters) - Major shareholders of top Chinese banks including ICBC, and companies including Sinopec, have pledged to either maintain their holdings or increase their stakes in the listed firms to try and support China's beleaguered stock markets.

The announcements come as China's securities regulator ordered shareholders with stakes of more than 5 percent to refrain from selling in the next six months in a bid to ease pressure on its stock markets.

China's stock markets have suffered from major sell-offs losing around a third of their value since June, prompting the government to unveil a series of market-supporting moves.

On Wednesday, the CSI300 index <.CSI300> of the largest listed companies in Shanghai and Shenzhen closed down 6.8 percent, while the Shanghai Composite Index (.SSEC) dropped 5.9 percent.

China's finance ministry and state investor Central Huijin Investment Ltd pledged not to reduce their shareholdings in the country's Big Four banks - Industrial and Commercial Bank of China Ltd (ICBC) <601398.SS>(1398.HK), China Construction Bank <0939.HK><601939.SS>, Agricultural Bank of China Ltd (1288.HK)<601288.SS> and Bank of China Ltd <601988.SS>(3988.HK).

Sinopec Corp <0386.HK><600028.SS>(SNP.N), Asia's largest oil refiner, said in a filing on Wednesday that its controlling shareholder Sinopec Group had increased its stake in the listed company by buying 46 million A shares in Shanghai, or 0.04 percent of the total issued share capital.

China Railway Construction Corp Ltd's <601186.SS><1186.HK> controlling shareholder bought 1.15 million shares in the secondary market, lifting its stake in the company to 61.34 percent, the company said in a filing on Wednesday.

Electric vehicle maker and Warren Buffett-backed BYD Co Ltd's <002594.SZ>(1211.HK) controlling shareholder and executives plan to lift holdings in the company.

In a bid to boost market confidence, China's fourth-largest broker Haitong Securities Co Ltd <600837.SS> <6837.HK> said it planned to buy back shares for up to 21.6 billion yuan($3.5 billion) within six months.

(Reporting by Lee Chyen Yee in Singapore, Twinnie Siu and Christina Lo in Hong Kong,Editing by Elaine Hardcastle)