MOSCOW, January 11 – Two cases have been lodged with the Hague-based Permanent Court of Arbitration against Russia by Ukrainian oil and gas companies, according to court records released on Monday.

Both cases were filed on June 15, 2015, under the 1998 bilateral treaty between Russia and Ukraine.

The first legal action was brought by Ukrnafta, one of Ukraine's largest oil and gas companies.

The second action was brought a number of Ukrainian companies, including Stabil, Rubenor, Rustel, Novel-Estate, PII Kirovograd-Nafta, Crimea-Petrol, Pirsan, Trade-Trust, Elefteria, Satek, Stemv Group. 

Switzerland is indicated as the seat of arbitration in both cases.

Russia so far has filed two letters with the court raising objection to its jurisdiction and the admissibility of the claims. Moscow has not appointed any representatives yet, according to the court.

In the meantime, the court announced last week about proceedings commenced by Ukrainian billionaire Igor Kolomoisky against Russia over an airport in the breakaway region of Crimea.