HONG KONG - Hong Kong's Independent Commission Against Corruption on Thursday arrested the chairmen of Sun Hung Kai Properties, brothers Raymond and Thomas Kwok, on suspicion of corruption, the company said.

The Kwoks own US$18.3 billion (S$23 billion), the second-biggest family fortune in Hong Kong after Asia's richest man, Li Ka-shing, founder of rival developer Cheung Kong (Holdings), according to Forbes magazine.

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The company issued a statement saying the Kwoks would continue with their duties as chairmen and managing directors of Sun Hung Kai, Asia's largest developer by market value, and that normal business operations would not be affected.

The ICAC also said it had arrested a former senior government official, whom the South China Morning Post identified as former chief secretary Rafael Hui, who has worked as a special adviser to Sun Hung Kai.

The ICAC announced on its website that the people arrested, whom it did not identify, were "alleged to have committed offences under the Prevention of Bribery Ordinance and misconduct in public office".

"Two senior executives of a listed company in Hong Kong and a former principal official of the Hong Kong Government have been arrested for suspected corruption," the ICAC said in a statement.

Gary Plowman, a former government prosecutor, said he had been to the ICAC and was representing one of the arrested parties whom he declined to identify.

"Nobody has been charged," Plowman said. As for what happened next, that was "a very good question".

"We react, we're not proactive. We are reactive in these situations," he said.

The ICAC was set up in 1974 to root out what was seen as widespread corruption in the Hong Kong government at the time, especially in the police.

It acts as a law-enforcement agency, able to arrest and detain suspects, and prosecutes cases in conjunction with advice from the Department of Justice.