Russian fertilizer producer Acron will challenge the merger between potash companies Silvinit and Uralkali in court, as it ups its opposition to the deal.

A spokesperson for Acron, which owns 8% of Silvinit, said it had lodged a claim at a court in Perm, east of Moscow, ahead of a Feb. 4 vote on the deal by shareholders.

Uralkali said it would fight the claims, saying they were "without merit." The Acron spokesperson declined to elaborate on the detail of the claims.

A merger of Silvinit and Uralkali to create a Russian potash mining giant was engineered by billionaire tycoon Suleiman Kerimov, who bought controlling stakes in both companies alongside associates last summer.

Potash, a key ingredient in fertilizer, has emerged as a valuable commodity in a world struggling to feed a growing population while battling droughts and floods.

Moscow's Investor Protection Association said late last year Silvinit shareholders should vote against the deal as it strongly favored investors in Uralkali.

Acron voted against the deal at a board of directors meeting last year.

Kerimov, who serves in Russia's upper house of parliament, will be left with 16% of the combined group after the deal is completed.