Gov. Sergey Aksyonov, the Kremlin-appointed head o Crimea, said that overnight Ukrainian strikes killed four people and wounded 28 others. He did not specify the target of the attack.

He later wrote on social media that local gas stations would halt all sales to non-state companies and individuals for an undefined period.

“Fuel will be sold only to government agencies that ensure the functioning and security of the Republic of Crimea,” Aksyonov said. “I ask everyone to remain calm and to only trust official sources of information.”

Ukrainian forces have repeatedly targeted fuel supplies to Crimea in recent weeks, triggering the worst energy crisis in the region since it was illegally annexed by Russia in 2014.

Ukrainian President Volodymyr Zelenskyy said in a statement Sunday that a Crimean oil depot, as well as an oil transport facility in Russia’s southern Krasnodar region were among the targets. He described the attacks as part of Ukraine’s “long-range sanctions” against Russia’s energy infrastructure.

“Russia understands only strength, and our long-range strength is certainly working for peace,” he wrote.

Russian officials in Krasnodar reported earlier Sunday that a drone strike sparked a fire at a Black Sea oil terminal in the village of Chushka. They said that Ukrainian attacks struck a ferry, killing one person.

Motorists struggle to find fuel

The Crimean peninsula has had periodic fuel shortages from Ukrainian strikes before, but the current crisis is the worst since its 2014 annexation.

At the end of May, authorities restricted the sale of gas to 20 liters (5 1/3 gallons) per vehicle owner per week, using prepaid coupons. Those were snapped up immediately following their release on an official messaging app channel, and motorists lined up for hours, waiting to refuel.

Social networks have been abuzz with requests and advice on where to find fuel, and authorities launched a hotline for tourists in the area who have found themselves trapped.

Some motorists bring their own gas from Krasnodar and elsewhere via the Kerch bridge, but they are restricted to carrying 100 liters (about 26 1/2 gallons) per vehicle. Some speculators are selling gas at double the market price.

In a rare public acknowledgment, the Kremlin has recognized the scope of the problem and promised to address the issue quickly.

However, Ukraine’s successes have highlighted its ability to inflict painful damage on Russia and change the course of the conflict while Moscow’s advances recently have ground to a near halt. On June 11, Russia’s full-scale invasion of Ukraine reached its 1,569th day, surpassing the duration of World War I.