OAO Novatek, the latest hot stock offering from Moscow, is tempting investors with a rare chance to cash in on Russia's vast natural gas reserves.

But some fund managers and analysts warn the enthusiasm for this deal could be blinding buyers to the risks in a sector where the Kremlin has been tightening its grip.

They point to OAO Gazprom, the state-controlled giant that is at once Novatek's biggest competitor and its sole route to market, thanks to its control of the national pipeline network. In the wake of the partial nationalization of oil giant OAO Yukos, they say investors need to tread cautiously when it comes to independents like Novatek in the strategic energy industry.

A flagship of Kremlin efforts to reassert control in the energy sector, Gazprom has in the past used its leverage to bring smaller competitors to heel.

One independent nearly lost its production license in a conflict with the gas giant earlier this year, then found its pipeline access cut sharply. Ultimately, the company ceded a 51 percent stake to Gazprom, which argued that it had been unfairly diluted out of a shareholding in the company several years ago.

"For someone who's been in Russia a long time . . . it's harder to get comfortable with the [Novatek] story given what you know about Gazprom," said Ian Hague, a principal at Firebird Management LLC, which has invested in Russia since the early 1990s and counts Gazprom as one of its key holdings.

Bulls on the stock say Novatek has a symbiotic relationship with the gas giant, helping supply the domestic market so Gazprom can concentrate on more lucrative exports. The two companies signed a broad cooperation deal just days before Novatek and its bankers began pitching the share issue in the United States and Europe. A Novatek spokesman declined to comment this week, citing regulatory restrictions related to the offering.

Publicly, Gazprom officials confirm they are on good terms with Novatek.

At the same time, the first "risk factor" listed in Novatek's prospectus warns that the Russian government, through Gazprom, "effectively controls our industry and may determine that independent gas producers such as ourselves should not have a significant role." Antitrust regulators effectively scuttled a $1 billion deal Novatek lined up last year with Total SA of France.

Despite the stern warnings, many investors seem willing to take the risk. People close to the deal say demand for Novatek will likely be strong enough to price the stock near the top of the proposed price range and value the 20.7 percent stake on offer at nearly $1 billion, which would make it one of the largest Russian offerings ever.

"We think there are good arguments to believe that Gazprom will not hurt them because [Novatek] has production capacity in areas where Gazprom's is declining," said Jochen Wermuth, manager of the $150 million Greater Europe Fund.

Russia has the largest gas reserves in the world, but investors have had little opportunity to buy into them because of complex restrictions on foreign ownership of Gazprom stock. The government has promised to lift those limits by the end of the year.

Though small by Russian standards, Novatek's 20.67 trillion cubic feet of gas reserves at the end of 2004 were nearly 1 trillion cubic feet bigger than Chevron Corp.'s 19.68 trillion cubic feet.

Fueled by rising gas prices and demand inside Russia, Novatek plans to double production by the end of the decade, making it a rare growth story in a sector dominated by slower-moving behemoths. Novatek's dramatically lower costs also make it a tantalizing alternative to Gazprom.

"It's a very interesting opportunity," said Agne Zitkute, an Eastern Europe specialist at Pictet Asset Management in London who expects to buy stock in the offering.

But in the wake of the partial nationalization of Yukos, an oil giant that was once a darling of foreign investors and that seemed for years to enjoy good relations with the authorities, some Moscow veterans warn the market's memory could be too short. Already, Russian stocks have rebounded to near-record levels after plunging with the dismantling of Yukos late last year.

"If one takes a long perspective and begins to question where the assets came from and questions the relationship with Gazprom, one can become quite nervous," said James Fenkner, managing partner in Red Star Asset Management, a newly opened hedge fund focusing on the region. He would not comment on fund positions.

There is no sign that Novatek could be the target of anything like the all-out assault that the Kremlin mounted against Yukos -- whose main shareholder was perceived as a political threat, something Novatek isn't.

But prosecutors in Novatek's home region in northern Russia are pursuing a criminal case involving a government-sponsored fund that was a shareholder and creditor until early this year. Novatek is not implicated in the case, but a member of its board of directors, who also served as head of one of its key units, sits on the board of the fund being investigated.

Prosecutors aren't targeting him, but he recently stepped down as deputy governor of the region.