UC Rusal investors suffer as historic IPO turns sour

* Shares tumble 7 percent, now 30 percent below offer price

* Fall comes despite recent rise in aluminium price

MOSCOW, Feb 18 (Reuters) - Shares in UC RUSAL  tumbled nearly 7 percent on Thursday, meaning the world's largest aluminium producer has shed more than a third of its IPO price in a month.

Ever-present uncertainties surrounding the group's CEO and major shareholder Oleg Deripaska which caused retail investors to be banned from the original float are among the reasons for the slide, traders and fund managers said.

The fall has come despite the price of aluminium rising by around $100 a tonne since Feb. 5 to trade around $2,100 a tonne.

RUSAL floated around 10 percent of its stock amid great fanfare in late January -- raising $2.2 billion to pay down debt while becoming the first ever non-Asian firm to list in Hong Kong.

"Most of the fund managers don't like the stock .. The gearing ratio is very high. There's a lot of uncertainty about the aluminium business in Russia," said one Hong Kong dealer, on condition of anonymity.

Alfred Chan, chief dealer at Cheer Pearl Investments, said some funds were obviously keen to get rid of the stock.

"There's a sell-off by some big fund ...They've been waiting so long to unload it and there's been no turnaround in the business. The turnover is very heavy. Whoever's selling it is a big boy, there are no small investors involved in this stock," he told Reuters.

Other traders cited the recent results of Norwegian aluminium group Norsk Hydro , which missed market forecasts for the fourth quarter on Wednesday but said it expected modest growth for 2010.

The Russian company's shares tumbled 9 percent on their debut as previously favourable market conditions suddenly crumbled - and the latest fall sees the stock some 30 percent below the HK $10.8 flotation price at HK $7.4.

RUSAL's IPO, which had been expected to spark a stampede by Russian firms to list in Hong Kong, was backed by New York hedge fund guru John Paulson, Hong Kong's richest man Li Ka-shing and blue-blooded financier Nathaniel Rothschild -- all now sitting on heavy losses.

(Reporting by John Bowker in Moscow and Sui-Lee Wee in Hong Kong; Editing by Jason Neely)