Hong Kong - China has clamped down on permits to visit Macau after seeing huge amounts of money flood into casinos in the resort, some of them American-owned, a news report said Thursday.

People in the wealthy southern province of Guangdong that neighbours the former Portuguese colony are now limited to only one trip every three months, the South China Morning Post reported.

The move is the latest in a series of crackdowns aimed at stopping money pouring out of China into Macau that began in June with a limit on one visit for people from Guangdong, Macau's biggest source of gamblers.

The restrictions have already seen the number of visitors from Guangdong dropping by half since earlier this year, travel agents quoted by the newspaper said.

China is believed to be concerned at the amount of money flooding out of the country into Macau's casinos which now rake in more money than the world-famous Vegas Strip in Las Vegas.

Macau, a densely populated territory of 450,000 people, is the only place in China where gambling is legal and draws millions of gamblers a year, mainly from China, Taiwan and Hong Kong.

Its gaming industry has boomed since 2003 when it was opened up to overseas operators, ending a 40-year monopoly by casino tycoon Stanley Ho.

It now has 4,311 gaming tables and 13,552 slot machines, compared with 424 and 814 in 2003, respectively. The number of casinos has rocketed from 11 to 29.

Casinos include several new upmarket resorts owned by Las Vegas-based companies, such as the 2.4-billion-US-dollar Venetian Macao Resort, the Sands casino and Steve Wynn's Wynn casino.

Gambling revenue has grown at a rate of more than 20 per cent a year, and in 2006, Macau officially became the most profitable gambling centre in the world, generating 7 billion US dollars in gambling revenue, around 1 billion US dollars more than the Vegas Strip.

Macau was a Portuguese colony until 1999 when it reverted to Chinese rule. It maintains a border and a separate economic and political system to mainland China. (dpa)