STOCKHOLM (Bloomberg) — Bermuda-based West Siberian Resources Ltd., the Stockholm-traded oil producer operating in Russia, dropped the most in three months in Stockholm trading after saying sales in Russia fell short of analyst estimates.

West Siberian fell as much as 0.38 krona, or 7.2 percent, to 4.92 kronor, the biggest one-day decline since November 22. The stock traded at 4.95 kronor as of 12:45 p.m. local time, giving the company a market value of 5.89 billion kronor ($940 million).

"The company got paid less for its product than expected," said John Helgesson, an analyst at Swedbank AB with a "buy" rating on the shares. "I had expected a higher percentage of oil sold nationally."

Helgesson said he expected higher sales in Russia because of climbing export duties on crude. West Siberian's tax charges for the fourth quarter were $6.62 million, compared with a net tax gain a year earlier.

The oil producer yesterday posted net income of $4.82 million for the fourth quarter, compared with a net loss of $1.54 million a year earlier. Sales more than doubled to 134.4 million as output grew.

"The operational success was however not fully reflected at the bottom line in 2007," managing director Maxim Barski said in a statement, citing "a large increase" in production taxes.

To curb the cost burden from Russia's tax system, which charges lower export duties on oil products than on crude, West Siberian last month agreed to acquire closely held OAO Alliance Oil Co. for about $1.5 billion in stock. The transaction will give West Siberian access to Alliance's Khabarovsk oil refinery in Russia's Far East.