The peninsula, which Russia seized in 2014, was once a secure base that Moscow’s forces have used to launch attacks, and it was a staging ground for the start of the February 24 invasion.
But in recent days, explosions have destroyed several Russian planes at an air base in Crimea, and munitions blew up on Tuesday.
Ukrainian authorities have stopped short of publicly claiming responsibility, but Ukrainian president Volodymyr Zelenskiy alluded to Ukrainian attacks behind enemy lines after the most recent blasts on Tuesday, while Russia blamed “sabotage”.
The spate of attacks represented the latest setback for Moscow, which began its invasion with hopes of taking the capital of Kyiv and much of the country in a lightning blitz, but soon became bogged down in the face of fiercer-than-expected resistance from Ukrainian forces.
As the war nears the half-year mark, the sides are now engaged in a war of attrition, fighting village to village, largely in the country’s east.
The attacks in Crimea could open a new front that would represent a significant escalation in the war and further stretch Russia’s military resources.
But it was not clear whether the attacks in Crimea would unblock the stalemate, as Ukrainian and Russian forces grind each other down in a war that has driven millions from their homes, disrupted food supplies worldwide and occasionally raised concerns about a nuclear accident.
On Thursday, UN secretary-general Antonio Guterres plans to travel to Ukraine for a meeting with Mr Zelenskiy and Turkish president Recep Tayyip Erdogan to discuss getting out grain shipments that are critical to feeding the world.
They are also expected to talk about a possible fact-finding mission to the Russian-controlled Zaporizhzhia nuclear power plant, which Moscow and Kyiv have accused each other of shelling.
Tuesday’s explosions and fires ripped through an ammunition depot near Dzhankoi in Crimea, leading to chaotic scenes when about 3,000 people had to be evacuated.
As a vivid reminder of Russia’s vulnerability in Crimea, the peninsula’s regional leader, Sergei Aksyonov, said that authorities were still fighting the fires on Wednesday with a helicopter, as munitions continued to detonate.
He said that a search for the perpetrators of the attack was under way.
The Kommersant business paper also reported explosions on Tuesday at a base in Gvardeyskoye. By Wednesday, there still was no comment from the Russian authorities.
A week earlier, Russia’s military came under pressure on the peninsula when Ukraine said nine Russian warplanes were destroyed following explosions at Crimea’s Saki air base.
The massive explosions sent plumes of smoke rising over nearby beaches and caused sunbathers to flee.
At the time, Moscow suggested that the blasts were accidental, perhaps caused by a careless smoker, an explanation that drew mockery from Ukrainian authorities who hinted at their involvement in the attack but did not directly claim responsibility.