KYIV, Ukraine (AP) — An explosion Saturday caused the partial collapse of a bridge linking the Crimean Peninsula with Russia, damaging a key supply artery for the Kremlin’s faltering war effort in southern Ukraine. Russian authorities said a truck bomb caused the blast and that three people were killed.

The speaker of Crimea’s Kremlin-backed regional parliament immediately accused Ukraine of being behind the explosion, though Moscow didn’t apportion blame. Ukrainian officials have repeatedly threatened to strike the bridge and some lauded the destruction, but Kyiv stopped short of claiming responsibility.

The explosion risked a sharp escalation in Russia’s eight-month war, with some Russian lawmakers calling for Russian President Vladimir Putin to declare a “counterterrorism operation” in retaliation, shedding the term “special military operation” that had downplayed the scope of fighting to ordinary Russians.

The Kremlin could use such a move to further broaden the powers of security agencies, ban rallies, tighten censorship, introduce restrictions on travel and expand a partial military mobilization that Putin ordered last month.

Hours after the explosion, Russia’s Defense Ministry announced that the air force chief, Gen. Sergei Surovikin, would command all Russian troops in Ukraine. Surovikin, who over the summer was placed in charge of Russian troops in southern Ukraine, had led Russian forces in Syria and was accused of overseeing a brutal bombardment that destroyed much of the city of Aleppo.

Moscow, however, continues to suffer battlefield losses.

On Saturday, a Kremlin-backed official in Ukraine’s Kherson region announced a partial evacuation of civilians from the southern province, one of four illegally annexed by Moscow last week, amid an ongoing Ukrainian counteroffensive.

Kirill Stremousov told Russia’s state-run RIA Novosti agency that young children and their parents, as well as the elderly, could be relocated to two southern Russian regions because Kherson was getting “ready for a difficult period.”

The 19-kilometer (12-mile) Kerch Bridge across the Kerch Strait that links the Black Sea with the Sea of Azov is a tangible symbol of Moscow’s claims on Crimea and has provided an essential link to the peninsula, which Russia annexed from Ukraine in 2014. The $3.6 billion bridge, the longest in Europe, opened in 2018 and is key to sustaining Russia’s military operations in southern Ukraine.

While Russia seized the areas north of Crimea early during its invasion of Ukraine and built a land corridor to it along the Sea of Azov, Ukraine is pressing a counteroffensive to reclaim those lands.

Russia’s National Anti-Terrorism Committee said a truck bomb caused seven railway cars carrying fuel to catch fire, resulting in the “partial collapse of two sections of the bridge.” A man and a woman in a vehicle on the bridge were killed by the explosion, Russia’s Investigative Committee said. It didn’t say what happened to the third victim or the truck driver.

The blast occurred even though all vehicles crossing the bridge undergo state-of-the-art checks for explosives, drawing a stream of critical comments from Russian war bloggers who urged Moscow to retaliate by striking Ukrainian civilian infrastructure.

The truck that exploded was owned by a resident of the Krasnodar region in southern Russia. Russia’s Investigative Committee said the man’s home was searched and experts were looking at the truck’s route.