Hong Kong  - A surge in Macau's population spurred by the boom in its casino industry is bringing increasing growing pains to the Chinese territory, government officials said Friday.

According to official statistics, the population of the former Portuguese colony, already the most densely populated place in the world, rose by 4.98 per cent in the 12 months ending in June and now stands at 551,900.

The Statistics and Census Bureau forecast the population would continue to grow by 4.6 per cent a year and reach 644,000 residents by 2011.

Government experts said the rise is because of an increase in imported labour flooding Macau to man its casinos and hotels and not an increase in births.

At the end of June, imported workers accounted for 98,505 of the population - an increase of more than 23,000 on the year before.

Experts said this growth is putting a strain on land, infrastructure and the electricity supply of the tiny Chinese enclave, which has a population density of 18,900 people per square kilometre, compared with 6,736 in neighbouring Hong Kong.

"It would be hard for Macau to sustain a much bigger population with its current infrastructure and land resources," Professor Zeng Zhonglu of Macau's Polytechnic Institute said in a report in the local media.

Macau's casino industry was overhauled in 2003, allowing upmarket Las Vegas-owned casinos to compete for the first time with the dozen existing casinos owned by tycoon Stanley Ho's monopoly.

But in April, Chief Executive Edmund Ho announced a series of tough measures aimed at curbing the spiralling growth of the casino industry.

They included not granting new licences for casinos, gaming tables and slot machines and barring casino operators from using reclaimed land for further development.

Macau, which reverted back to China in 1999 after 449 years of Portuguese rule, is the only place in China where gambling is allowed.

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.

They include several new upmarket Las Vegas-style resorts, such as the 2.4-billion-US-dollar Venetian Macao Resort. (dpa)