China's Postal Savings Bank says some retail investors opt out of mainland listing

BEIJING, Dec 4 (Reuters) - Postal Savings Bank of China said investors had opted out of paying for 3% of shares on offer in its Shanghai listing - a rare development that underscores growing concerns over problems in China's banking system.

Nearly all were retail investors, PSBC said in a statement late Tuesday.

PSBC, China's biggest bank by number of branches, is seeking to raise up to 32.71 billion yuan ($4.7 billion) with the share sale, which includes a greenshoe option of 15%.

Unlike other major IPO markets, in mainland China where IPOs and share sales are usually heavily subcribed to, investors are not required to pay before getting an allocation.

Underwriters of the share sale will pick up the unsold shares. ($1 = 7.0389 Chinese yuan) (Reporting by Cheng Leng in Beijing and Engen Tham in Shanghai; Editing by Edwina Gibbs)