Agricultural Bank of China raised US$22.1 billion as it exercised an over-allotment option to surpass the Industrial and Commercial Bank of China as the world's biggest initial public offering.

The bank sold a further 3.34 billion shares at the issue price of 2.68 yuan each in Shanghai, it said yesterday in a filing to the Shanghai Stock Exchange. This boosted its Shanghai part of its IPO to 68.5 billion yuan (US$10 billion).

The Beijing-based bank went public in Shanghai on July 15 before being listed in Hong Kong a day later. The Hong Kong IPO marked the international part of its mega-sized dual-listing as that market is open to global investors.

AgBank raked in US$19.2 billion in its dual-listing in Shanghai and Hong Kong then. The bank could take in up to US$22.1 billion by executing an over-allotment option within 30 days of trading.

Its underwriters dropped the greenshoe option, in which underwriters could buy back the over-allotted shares to shore up prices if shares fall below the offer price.

The bank's shares debuted weakly in Shanghai, hovering just above its offer price of 2.68 yuan. Its shares have been testing the 2.68 yuan level in the first trading week and last week since its debut. Its shares ended at 2.71 yuan yesterday in Shanghai, up 0.74 percent. The Shanghai Composite Index rose 2.1 percent to 2,661.71.

Many investors were worried that AgBank's giant share offering would stretch market liquidity, divert money away from stocks of rival banks and put other big listings on hold in the bumpy Shanghai market.

In July, the bank's yuan-backed A shares were nearly 10 times oversubscribed by retail investors - considered low compared with rivals that debuted in a bullish market. The Shanghai index has lost 22 percent this year and is the worst performer among the world's 10 biggest markets.

China International Capital Corp, Deutsche Bank, Goldman Sachs, JPMorgan Chase & Co, Macquarie Group and Morgan Stanley arranged the bank's IPO. It is the last of the big five state-owned banks to list.