yakuza gangsters will not be celebrating.

When the toasts are raised here next year at the opening of the world's tallest communications tower, the Tokyo Sky Tree, yakuza gangsters will not be celebrating.

"The mob cannot come here," said Mr Toru Hironaka, a lawyer who leads a legal team retained by the tower's developers to bar crime syndicates from the project.

The ban is part of an effort by the Japanese government and business community to sever the deep-rooted ties between organised crime and corporate Japan, especially in the construction industry.

As part of the crackdown, a top crime boss of Japan's largest crime syndicate, the Yamaguchi-gumi, was arrested on Thursday on charges of extorting ¥40 million ($622,200) from a construction company in the western city of Kyoto.

"Organised crime is threatening Japan's entire economy," said Mr Kohei Kishi, director of the organised crime division of Japan's National Police Agency. "And they have deep roots in construction."

The National Police Agency and other government departments are pressuring businesses to stamp out mafia links - the country's Finance Ministry, for example, has directed banks to step up safeguards to cut off loans to mob-related companies and deny bank accounts to individuals with known gangster ties.

Yakuza bosses pressure developers to pay "protection money" to cover construction projects or use front companies to win lucrative contracts, police say.

Next month, Tokyo is set to ban any company or individual affiliated with the yakuza from city contracts, along with threats of penalties and public disclosure for companies with mafia ties.

But the mob is threatening to fight back. Last month, a gunshot was fired into the wall of a construction site linked to one of Japan's biggest contractors. It was the fourth shooting at construction sites in Tokyo this year.