A new front opened in Russia’s war on Ukraine that highlights the vulnerability of oil exports from the nation’s western ports, after reports of drone attacks against facilities on the Baltic coast.

Last week, the first ever Ukrainian drone reached Russia’s Leningrad region, approximately 1,000 kilometers (620 miles) from the border. The aircraft was downed over the privately-owned Petersburg Oil Terminal without causing damage, according to Russian authorities.

A second drone attack on Sunday, which an official with knowledge of the matter said was organized by Ukraine’s secret services, was more disruptive. It caused a fire that shut down a Novatek PJSC gas-condensate plant in port of Ust-Luga that supplied fuel to the Russian army, they stated with the condition of anonymity.