The Hong Kong share sale proved extremely popular

Bank of China, whose shares began to trade on June 1, said backers of the flotation had taken up an option to sell an additional 3.8 billion shares.

This increases the total amount of money raised to about $11.2bn.

Bank of China is eyeing up mainland China's biggest-ever domestic float, hoping to raise 20bn yuan ($2.5bn).

China's second-largest lender has seen its Hong Kong stock rise 20% since its shares began trading.

Institutional backers of the float, including Goldman Sachs and UBS, said they had issued more shares on Wednesday, valued at 2.95 Hong Kong dollars (38 cents) each.

The share sale has been heavily oversubscribed.

The bank said it would issue no more than 10 billion shares in China, with reports saying it could be as early as July.

China's principal foreign exchange bank said the timing of the sale and a Shanghai flotation would depend on market conditions and regulatory approval.

Application submitted

Combined with the cash raised from its Hong Kong flotation, the bank hopes to stay within its 20bn yuan cap on planned fundraising.

China recently began allowing domestic initial public offerings (IPOs) after a year-long block, and Bank of China's domestic listing would be the largest to date if it raises more than $1.5bn.

The firm said it had submitted an application with the China Securities Regulatory Commission (CSRC) for the go-ahead to proceed with a mainland share offering.