LOCKED-UP shares worth about 11 percent of the combined value of the A shares listed on the Shanghai and Shenzhen exchanges will become tradable this week, a record level unlikely to be ever surpassed.

Shares in 29 firms worth about 2 trillion yuan (US$29.85 billion), or 10.97 percent of the market capitalization of the A shares listed on the two exchanges, will become tradable between today and Friday, raising concerns about supply and volatility.

Some of the firms' closing share prices last Friday were well above their initial public offering price, which may encourage investors to engage in profit-taking, Southwest Securities chief analyst Zhang Gang said.

About 162 billion shares in nine companies listed on the Shanghai Stock Exchange will become tradable while 998 million shares in 20 companies listed on the Shenzhen bourse will be able to do so, according to the brokerage's data.