"There is no official pronouncement of what it means to breach sanctions," Draghi said. "Nobody has ever said anything about whether rubles payments breach sanctions or not."

Draghi said it's "such a gray zone." He said Germany's biggest company has already paid in rubles and that most gas importers have already opened accounts in the Russian currency.

The 27-member economic bloc has been left scrambling to secure supplies after President Vladimir Putin said in March that Russia would only accept payment in rubles.

Draghi said it's "such a gray zone." He said Germany's biggest company has already paid in rubles and that most gas importers have already opened accounts in the Russian currency.