President Vladimir V. Putin, who was traveling to a meeting of gas exporters in Iran, did not immediately comment. He was unlikely to take kindly to Ukraine disrupting life for all of Crimea, however, given that he has made its absorption into Russia something of a personal project.

Sergei V. Aksyonov, the Kremlin-appointed prime minister of the Crimean Republic, was more exercised, calling the power cutoff “a terrorist act” in a statement on Monday.

“I would urge Crimeans to be patient and to see what our situation is,” Mr. Aksyonov said. “Nobody will be allowed to blackmail us in order to solve any issues.”

Ukraine still claims the peninsula, and its senior officials have been perturbed that its seizure by Russia has seemingly dropped off the international agenda, rating a fleeting mention at best whenever the crisis over fighting in southeastern Ukraine is discussed.

The issue of supplies coming from Ukraine has been a repeated source of tension, as food, water and electricity still flow from the mainland to the peninsula. A major irrigation canal was shut down in 2014, but significant rainfall and other local sources prevented serious damage to crops this year. In September, Tatar and other activists tried to blockade the main road leading from Crimea to Ukraine, disrupting food supplies.

Crimea’s only other surface link to the outside world is a ferry line to Russia, with limited capacity. Russia plans to build an enormous bridge, but that would not be completed for at least three years.