RusPetro PLC (RPO.LN), a U.K. oil and gas company focused on drilling in Siberia, Russia, Wednesday raised approximately GBP163 million through a conditional initial public offering on the London Stock Exchange.

The IPO, the first significant London listing for 2012, values RusPetro overall at approximately GBP440 million. RusPetro Thursday said in a statement it had placed 121,542,000 new ordinary shares, representing around 59% of the company's shares, at 134 pence per share. The price is towards the bottom end of an informal range in a bookbuilding exercise launched on Tuesday, according to research from FoxDavies.

The IPO will be closely watched because of the drought in London-based capital markets activity over the past two quarters. Although a number of companies are waiting to come to market, fears over the ongoing euro zone debt crisis and the broader European economic outlook have weighed heavily on IPO prospects, with the market almost drying up.

Ruspetro's post-offer free float is expected to be 40%.

By 1215 GMT shares were trading down by over 4% at 128 pence in a higher broader London market.

"I am extremely proud that RusPetro has completed a premium listing on the London Stock Exchange at this time," Don Wolcott, RusPetro's chief executive, said in a statement. "At a time when very few IPOs have been completed, our successful listing shows that investor demand is still there for high-quality stories such as our own."

RusPetro plans to spend the bulk of the IPO proceeds on well drilling and infrastructure development in Siberia, and the remainder on paying down debt, it said in the press release.

According to a report by Interfax, the conditional IPO saw the bulk of the shares placed with around 10 investors, and the free float being shared between three funds, leading to low liquidity in the stock. A spokesman for the company declined to comment. People familiar with the process said the IPO had been well-subscribed by long-only institutional investors.

RusPetro plans an unconditional listing on Jan. 24, it said in the prospectus.

RusPetro's development plans include over 100 wells by 2014 and building a new 27-kilometer pipeline to the Transneft pipeline.

The company, backed among others by Altera Capital, the investment fund whose managing partner Kirill Androsov is a former deputy chief of staff to Russia's prime minister Vladimir Putin, is the latest in a line of Russian companies which have recently floated in London. Recent London-based IPOs of Russian companies include precious metals miner Polymetal International PLC (PMTL.LN) and steel maker Evraz Group S.A.(EVRZ.LN).

Bank of America Merrill Lynch acted as global coordinator and sponsor, and Bank of America Merrill Lynch, Mirabaud Securities LLP and Renaissance Securities acted as joint bookrunners.

Chris Searle, a corporate finance partner at BDO LLP, said in a statement it was "too early" to say whether RusPetro's deal meant the IPO market was open again, but he said it was "encouraging."

He pointed out that the company will have a free float of 40%. London's blue chip FTSE 100 index recently changed its rules, requiring all companies trading on the index have at least a quarter of their shares freely tradable.

The move was in response to concern among institutional investors about the growing number of Russian oligarch-controlled companies listing on the index where control has been left substantially in the hands of a few dominant shareholders.

Concerns raised by investors include transparency, minority rights and effective governance.

RusPetro made an operating loss of $19.4 million on revenues of $23.7 million in the nine months to Sept. 30, 2011, according to listing documents.

-By Jessica Hodgson, Dow Jones Newswires; +44 7561 424788; jessica.hodgson@dowjones.com