HK shares drop to 18-month low, led by China stocks

* China Mobile drops on regulatory uncertainties

* China banks tumble amid economic slowdown fears

* Resource-relates shares plunge pressured by stronger dollar (Updates to close)

By Parvathy Ullatil

HONG KONG, Sept 11 (Reuters) - Hong Kong shares fell 3.1 percent on Thursday to their lowest close in 18 months as investors dumped shares in Chinese firms amid deepening fears of a global slowdown and a lack of growth-supportive policies from Beijing.

"Investors are extremely cautious on the global economic outlook," said Peter Pak, vice president with BOCI Research.

"And now with the U.S. government pledging large sums of money to bail out Fannie Mae (FNM.N: Quote, Profile, Research, Stock Buzz) and Freddie Mac

The U.S. government took control of the mortgage companies at the weekend in a bid to stave off further damage to the financial system, but many investors have had reservations about the deal, seeing it as a further sign of deep underlying troubles.

The benchmark Hang Seng Index .HSI closed down 611.06 points at 19,388.72, its lowest level since March 20, 2007.

Mainboard turnover rose to HK$69.6 billion ($8.9 billion) from HK$65.3 billion on Wednesday.

Chinese telecom stocks were also pressured by deepening concerns over the fallout from widespread industry restructuring and regulatory uncertainties.

China Mobile (0941.HK: Quote, Profile, Research, Stock Buzz), the world's largest wireless carrier, dropped 5.3 percent to a 15-month low of HK$77.00 as investors worried Beijing will impose regulations that are unfavourable to the firm but will benefit its rivals.

The company, which controls two-thirds of the country's cellular market, will have to begin testing a policy soon in two cities that will let users keep their cellphone numbers when they switch to another carrier, according to Chinese media reports.

But analysts expect that such a scheme, which may be rolled out in full by 2009, will be a one-way affair, barring users from retaining their numbers when they switch to China Mobile.

Shares in China Unicom (0762.HK: Quote, Profile, Research, Stock Buzz), China Mobile's smaller rival, tumbled 4.8 percent. China Netcom (0906.HK: Quote, Profile, Research, Stock Buzz), which is soon to be merged with China Unicom, dropped 4.5 percent.

Some analysts said that Thursday's sell-off in Chinese shares may have been spurred by speculation that H-share holders will have to start paying dividend tax.

"It's a bit strange to see investors react to that news because nobody really buys H-shares for their dividend yield. It just seems like another piece of bad news in an already weak market triggered a sell-off," said Steven Leung, director with UOB Kay Hian

Resources stocks took another beating on Thursday as an advancing U.S. dollar prevented a strong rebound in oil and other commodity prices even as Hurricane Ike whipped through the oil- and gas-rich U.S. Gulf.

Asia's largest oil & gas producer, PetroChina (0857.HK: Quote, Profile, Research, Stock Buzz), fell 4.4 percent while China Shenhua Energy (1088.HK: Quote, Profile, Research, Stock Buzz), the world's most valuable coal company, tumbled 6.4 percent.

Shares in China's top listed gold producer, Zijin Mining (2899.HK: Quote, Profile, Research, Stock Buzz), fell more than 10.5 percent on Thursday to a new 18-month low after gold prices slid.

The stock hit a low of HK$3.48 before recovering slightly to HK$3.51, down 9.8 percent. It has lost about 18 percent of its market value since Tuesday.

The China Enterprises Index .HSCE of top locally listed mainland Chinese firms slid 4.2 percent, tracking a 3.3 percent drop on the Shanghai Stock Exchange .SSEC.

Mainland banks slid as investors shrugged off the lower inflation data reported on Wednesday and focused on global economic worries.

China Construction Bank (0939.HK: Quote, Profile, Research, Stock Buzz) lost 3.9 percent while ICBC (1398.HK: Quote, Profile, Research, Stock Buzz) dropped 3.4 percent.

Chinese property stocks continued their downward drift on weak August property sales revenue and broker warnings of a gloomy property price outlook in top-tier Chinese cities.

China Overseas Land (0688.HK: Quote, Profile, Research, Stock Buzz) gave up 8.8 percent while Guangzhou R&F Properties (2777.HK: Quote, Profile, Research, Stock Buzz) slid 8.8 percent.

(Reporting by Parvathy Ullatil; Editing by Kim Coghill)