SHANGHAI, Aug 21 (Reuters) - Dozens of China-listed companies outlined plans over the weekend to purchase their own shares as regulators voiced support for share buybacks as part of measures to shore up a sinking stock market.

More than 30 companies including chipmaker Loongson Technology Corp and Xian Manareco New Materials Co have said since Friday that their controlling shareholders had proposed buying back shares because of confidence in the companies' future development and value.

China's securities regulator unveiled a package of measures on Friday aimed at boosting investor confidence in a market that had slid to nine-month lows.

They include cutting trading costs, supporting share buybacks and encouraging long-term investment.

Other companies that have announced share buyback plans include Shenzhen Kiwi Instruments Co and Chengdu Screeen Micro Electronics Co. (Reporting by Shanghai newsroom; Editing by Sonali Paul)