SHANGHAI, Oct 21 -- INDUSTRIAL & Commercial Bank of China Ltd raised US$19.1 billion in the world's biggest initial public offering after attracting orders equivalent to twice Citigroup Inc's market value.

China mainland's biggest bank sold 48.39 billion shares for HK$3.07 (39 US cents) and the equivalent in Chinese yuan, said two bankers involved in the IPO, who declined to be identified before the official announcement on Monday. The company may sell US$2.9 billion more stock once trading begins on Friday, Bloomberg News said.

ICBC raised the maximum amount sought as investors placed orders for more than US$500 billion of stock, betting the bank's 18,000 branches and a customer base bigger than Russia's population will be a proxy for the mainland's economic expansion. The IPO represents 14.8 percent of the company's shares and will value the Beijing-based bank at US$129 billion.

"The demand's a surprise, given the bank's main attraction is its size," said Ambrose Chang, who oversees US$1.6 billion of assets as chief investment officer of Daiwa SB Investments HK Ltd and who ordered ICBC shares. "It's a benchmark China bank stock and the sale came at the right time."

The Hang Seng China Enterprises Index of Chinese mainland shares traded in Hong Kong is at the highest level in more than 16 years, with the benchmark Hang Seng Index trading less than two percent from an all-time high.

Bank of China Ltd, the mainland's second-biggest, began selling stock in a US$11.2 billion IPO in May, when the China Enterprises Index fell 2.5 percent, the first monthly decline in 11. Shares of BOC have risen 15 percent since then.

ICBC's market value will rise to US$131 billion should the over-allotment option be exercised, and may top Mitsubishi UFJ Financial Group's US$135 billion if the stock gains once trading begins. That would make ICBC the world's fifth biggest bank.

New York-based Citigroup has a market value of US$248 billion.

"ICBC may have an upside of 10 percent on debut so it will trade at the industry average," said Liu Yang, who helps manage US$3 billion at Atlantis Asset Management Ltd in Hong Kong. "I'll probably sell if it goes above that. Loan growth is boring and management is ordinary. It's not even the best in the mainland, and there's no point comparing it with global lenders."

China's mainland, the world's fastest-growing major economy, has been trying to clean up banks saddled with bad debts that peaked at more than 30 percent of all loans in 2000, a legacy of unchecked lending to state companies and lax internal controls.

ICBC said it will use the proceeds from the sale to fund expansion.