Ukrainian drones are flying deep into Russia to strike oil facilities, sending up plumes of smoke that can be seen from space and bringing toxic rain to tourist destinations on the Black Sea.

The attacks are aimed at slashing Moscow’s oil exports, a key source of funding for its grinding invasion of Ukraine. But the economic impact is so far unclear, as the rise in oil prices from the Iran war, and a related easing of U.S. sanctions, have helped replenish the Kremlin’s coffers.