Moscow trading data for Friday show the Russian currency hit an all-time low against the U.S. dollar as the economy struggles under energy-related sanctions.

By midday in Moscow, the currency hit bottom with trade at 42 rubles to the U.S. dollar.

The Russian economy is burdened by Western sanctions targeting Russian energy companies. With oil trading below the $100 mark, sanctions were blamed for record inflation and a struggling ruble.

Igor Sechin, the head of Russian oil company Rosneft, said Thursday a lawsuit was filed in Luxembourg against the European Union in retaliation against sanctions.

"Our aim is to protect the interests of our shareholders," he said. "We will always protect their interests at any cost."

Sechin in August asked the Kremlin to use a national welfare fund to support its growing debt. The company's total production, meanwhile, is down to its lowest level in more than a year.

Sechin and the oil company he leads are targets of Western economic sanctions imposed in response to Russia's stance on crises in Ukraine, a former Soviet republic.

Russia's credit rating was downgraded last week by international ratings agency Moody's.