AMSTERDAM (Reuters) - Two Ukrainian energy companies have asked a U.N. arbitrator to award them compensation for investments they lost when Russia seized control of the Crimean peninsula, the Permanent Court of Arbitration (PCA) said on Monday.

The case, brought in June but only now made public, involves petrol stations owned by Ukrnafta and Stabil. It is the latest instance of investors asking international courts to compensate them for losses they blame on the Russian government.

Last year, Igor Kolomoisky, one of Ukraine’s richest businessmen, brought a case before the same court seeking some $15 million compensation from Russia for the loss of an airport he owned on the Black Sea peninsula.

Russia annexed Crimea in March 2014 after street protests in the Ukrainian capital forced a Moscow-backed president to flee.

In both cases, the plaintiffs alleged that the loss of their assets following Crimea’s annexation amounted to a violation of a bilateral investment treaty between Russia and Ukraine.

Russia has declined to contest both cases, saying the court has no jurisdiction over the matter. The court will hold hearings over whether it has jurisdiction in July.

In 2014, the PCA awarded a record $50 billion to former shareholders in oil company Yukos, which went bankrupt after controlling shareholder Mikhail Khodorkovsky ran foul of Russian leader Vladimir Putin and the government began demanding payment of huge sums in back taxes.

But a Dutch court last month set aside that ruling, saying the PCA had overstepped its jurisdiction. Both parties have pledged to continue the legal battle, in a sign that even a successful claim can be almost impossible to enforce.