Sistema, a minority shareholder in oil producer Bashneft and Bashkortostan's refinery complex, will seek to increase its stake in the region's oil companies after agreeing to manage them.

Sistema, which holds stakes of about 25 percent in the assets, signed a deal allowing it to manage them with their respective holding companies, it said Thursday.

"We will now work on the possibility of buying the remaining shares," CEO Vladimir Yevtushenkov said.

Sistema's holdings include Bashneft, Ufaorgsintez, Bashkirnefteproduct, Ufimsky, Novoil and Ufaneftekhim — all in the republic of Bashkortostan, it said.

Sistema will attempt to put Bashneft and the region's refineries into a "vertically integrated structure," Yevtushenkov said.

In August last year, a Moscow court found Bashkir companies guilty of illegal dealing in shares and said they should be transferred to the state.

The case is now under review by a higher court, although it has been complicated by the scrapping of a vague legal clause that officials used in attempts to confiscate property in April.

Analysts had expected the companies to eventually fall under the wing of state-controlled companies such as Gazprom and Rosneft as the state tightens its grip on the energy industry.

(Bloomberg, Reuters)