Ukraine Live Updates: Explosion Rocks Russian Air Base in Crimea

ODESA, Ukraine — A series of explosions rocked a key Russian air base on the Kremlin-occupied Crimean Peninsula on Tuesday, sending up huge plumes of smoke, killing at least one person and sowing confusion among local officials about what exactly had occurred.

As Russian and occupation officials scrambled to determine the cause, raising the terrorist threat level in the area, a senior Ukrainian military official with knowledge of the situation said that Ukrainian forces were behind the blast at the Saki Air Base on the western coast of Crimea.

“This was an air base from which planes regularly took off for attacks against our forces in the southern theater,” the official said, speaking on the condition of anonymity to discuss sensitive military matters. The official would not disclose the type of weapon used in the attack, saying only that “a device exclusively of Ukrainian manufacture was used.”

A Ukrainian attack on Russian forces in the Crimean Peninsula would represent a significant expansion of Ukraine’s offensive efforts, which until now have been largely limited to pushing Russian troops back from territories occupied after Feb. 24, when the invasion began.

It would also be an embarrassment for President Vladimir V. Putin of Russia, who often speaks of Crimea, which he illegally annexed from Ukraine in 2014, as if it were hallowed ground.

Ukraine possesses few weapons that can reach the peninsula, aside from aircraft that would risk being shot down immediately by Russia’s heavy air defenses in the region. The air base, which is near the city of Novofederivka, is nearly 200 miles from the nearest Ukrainian military position.

The senior Ukrainian official said the attack involved partisan resistance forces loyal to the government in Kyiv, but he would not disclose whether those forces carried out the attack or assisted regular Ukrainian military units in targeting the base, as has sometimes occurred in other Russian-occupied territories.

To reach targets deep behind enemy lines, Ukraine has increasingly turned to guerrillas in Russian-occupied territories, officials said. Partisans, for instance, have helped Ukrainian forces target Russian bases and ammunition depots in the Kherson Region, Ukrainian officials say.

Publicly, Ukrainian officials would not confirm the involvement of Ukraine’s military. Ukraine’s defense ministry said in a statement that it could not “determine the cause of the explosion,” and suggested that personnel at the base adhere to no-smoking regulations.

Other officials did not exactly deny that Ukraine was behind the explosion.

“The future of the Crimea is to be a pearl of the Black Sea, a national park with unique nature and a world resort, not a military base for terrorists,” Mykhailo Podolyak, a senior adviser to President Volodymyr Zelensky of Ukraine, said in a tweet. “It is just the beginning.”

Russia’s Defense Ministry said in a statement that the explosion was caused by the detonation of stockpiled ordnance for warplanes at the base. While the ministry offered no speculation about whether Ukrainian forces might have been involved, the decision by Crimea’s Kremlin-installed leader, Sergei Aksyonov, to raise the terrorist threat level to yellow suggested that officials were concerned about security on the peninsula.

“This measure is exclusively prophylactic, because the situation in the region is under full control,” Mr. Aksyonov said in a statement on Telegram.

In the eight years of Russia’s occupation of Crimea, the peninsula has transformed from a quiet southern Ukrainian beach destination into a major base of military operations. It is from there that Russian forces lunged into southern Ukraine in a lightning operation after Feb. 24 that gobbled up a huge swath of territory, including the neighboring Kherson Region, which Russian forces almost fully control.

The Saki air base is home to Russia’s 43rd Separate Naval Attack Regiment, which is part of the Black Sea Fleet. Ukraine’s military intelligence service has accused pilots from the regiment of committing war crimes by bombing civilian areas during the war.

Shortly after the explosion occurred, Mr. Aksyonov arrived at the scene. Standing in front of a large black plume of smoke, he said that a three-mile perimeter had been erected around the site of the base to protect residents.

“Unfortunately, one person died,” he said. “I express my most sincere sympathies to family and friends.” Crimea’s health ministry said that at least nine people had been injured.