Two billionaire brothers who control Asia's biggest property development company have gone on trial in Hong Kong's biggest ever corruption case.

Sun Hung Kai Properties (SHKP) co-chairmen Thomas and Raymond Kwok were among five people charged with a total of eight offenses, including conspiracy to offer advantages to a public servant and misconduct in public office, the Independent Commission Against Corruption (ICAC) said in a statement.

The two brothers are ranked fourth on the 2014 Forbes rich list.

Hong Kong's former chief secretary Rafael Hui, banker Francis Kwan and Thomas Chan -- responsible for land acquisitions for SHKP -- were the other men charged after one of the biggest anti-graft probes in the banking hub's history.

Hui, previously the city's No.2, faces charges related to misconduct in public office, including the acceptance of rent-free apartments and unsecured loans -- he's the highest-ranking former official to face trial in the city.

The ICAC revealed the offenses took place between 2000 and 2009 as investigators probed land sales overseen by Hui involving SHKP.

The case has caused a media frenzy in the city, where real estate is a local obsession. Sun Hung Kai, which helped to build some of the tallest buildings in the city's celebrated skyline, contributed to the Kwok brothers' estimated $18.3 billion fortune.

The brothers, who were arrested in March 2012, have protested their innocence.

"I can say that personally I have done nothing wrong. And I can vouch for Mr. Thomas Kwok that he has done nothing wrong either," Raymond Kwok said at a news conference on April 2012, referring to his brother.

"I hope this investigation will clear my name," he said at the time.

Hong Kong, a special administrative region of China, is considered to be one of the world's least corrupt territories. According to Transparency International's 2013 Corruptions Perceptions Index, Hong Kong is the 15th least corrupt territory in the world -- with the United States, by comparison, ranked 19th.