Russia's upper house of parliament, the Federation Council, on Wednesday approved amendments to a federal law which allow foreign ownership of shares in the world's largest natural gas producer Gazprom, news agencies reported.

The amendments end the division of the Gazprom share market and lift restrictions on the shares of the company that can be owned by foreigners. But the changes stipulate that state-controlled companies own a controlling stake of at least 50 percent plus one share in Gazprom, the Interfax and RIA Novosti news agencies reported.

The lower house of parliament, the State Duma, passed these amendments earlier this month. The amendments have yet to be signed by President Vladimir Putin to become law.

Foreigners seeking part of Gazprom have been restricted by a decade-old rule to owning the limited number of shares that trade on Western exchanges at a hefty premium. The changes are expected to attract foreign companies to buy into the natural gas giant, which produces 90 percent of Russia's gas and 20 percent of the world's total.

Gazprom has been in increasingly tense negotiations with Ukraine over gas supplies. The company said Wednesday it would sharply increase prices of gas delivered to Ukraine in 2006 and had threatened to cut supplies to Ukraine if the country rejected new terms of gas supplies.