Darkness washed over Crimea on Saturday after two pylons carrying power lines to the Black Sea peninsula were blown up, cutting electricity to nearly 2 million people.
"Crimea is completely cut off," Viktor Plakida, the director of Crimea Energy, told Russia's Tass news agency. "It's a blackout."
The Crimean Emergencies Ministry has declared a state of emergency and put its rescue teams on high alert.
Crimea was annexed by Russia following Ukraine's revolution and the ouster of its Kremlin-friendly president last year, but Ukrainian authorities have continued to supply power to the peninsula.
The two transmission towers in the southern Ukrainian city of Kherson were first damaged on Friday. Ilya Kiva, a senior officer in the Ukrainian police who was at the scene, said on his Facebook page that the towers had been "blown up."
Ukrainian activists, including Crimean Tatars, a local ethnic group opposed to Moscow's rule over the peninsula, clashed with police as they tried to block repair works on Saturday.
A video report by Crimean Tatar TV channel ATR shows Ukrainian police and soldiers donning kevlar and helmets, and armed with Kalashnikovs, shoving and arguing with the crowd of activists.
Photos shared on social media show Ukrainian and Crimean Tatar flags waving on some of the damaged lines. But it is unclear who exactly blew up the pylons.
Учасники блокади заперечують свою участь у підриві https://t.co/WRk6wiZUB3 pic.twitter.com/Qud4cfVhOd— Hromadske.TV (@HromadskeTV) November 22, 2015
Since Sept. 20, Crimean Tatar activists and other protesters, including many from the far-right nationalist group Right Sector, have blocked the flow of goods from mainland Ukraine to Crimea at all main road crossings into the peninsula. They are calling for a full economic and energy blockade.
Crimea remains heavily dependent on mainland Ukraine for electricity, gas and food, despite being under Moscow's control. Russia has no direct land route to Crimea; a single ferry boat is all that connects the two land masses.
But the activists' objectives are not only economic and political. One of their goals is to call international attention to human rights abuses, particularly the persecution of Crimean Tatars, since Russia's seizure of the peninsula. Several Crimean Tatars have reportedly been murdered, while others, as well as journalists, have allegedly been intimidated, kidnapped and beaten by Russian security services.
The central government in Kiev has neither formally supported nor criticized the blockade. The reaction among Ukrainians, politicians and activists has been mixed.
mixed reaction after electricity cut-off in #Crimea:some r happy UA finally done smth,others hate UA even more,most write ab panics at shops— Kateryna_Kruk (@Kateryna_Kruk) November 22, 2015
Every new minute of #Crimea's blackout eats away Ukraine's intl credibility/support too. I'm not sure the attackers thought this throu well— Maxim Eristavi (@MaximEristavi) November 22, 2015
The attack is likely to deepen tensions between Russia and Ukraine, which are at an all-time low over Crimea and the ongoing war in the country's eastern Donetsk and Luhansk regions.
Crimean authorities were reportedly able to partially restore power to the cities of Simferopol, Yalta and Saky using generators on Sunday. Meanwhile, the peninsula's hospitals used their backup power sources to stay operational, said Mikhail Sheremet, Crimea's deputy prime minister.
The Associated Press contributed reporting.