KYIV, Ukraine (AP) — Ukraine said Wednesday that nine Russian warplanes were destroyed in a deadly string of explosions at an air base in Crimea that appeared to be the result of a Ukrainian attack, which would represent a significant escalation in the war.

Russia denied any aircraft were damaged in Tuesday’s blasts — or that any attack took place. But satellite photos clearly showed at least seven fighter planes at the base had been blown up and others probably damaged.

Ukrainian officials stopped short of publicly claiming responsibility for the explosions, while mocking Russia’s explanation that a careless smoker might have caused ammunition at the Saki air base to catch fire and blow up. Analysts also said that explanation doesn’t make sense and that the Ukrainians could have used anti-ship missiles to strike the base.

If Ukrainian forces were, in fact, responsible for the blasts, it would be the first known major attack on a Russian military site on the Crimean Peninsula, which was seized from Ukraine by the Kremlin in 2014. Russian warplanes have used Saki to strike areas in Ukraine’s south.

Crimea holds huge strategic and symbolic significance for both sides. The Kremlin’s demand that Ukraine recognize Crimea as part of Russia has been one of its key conditions for ending the fighting, while Ukraine has vowed to drive the Russians from the peninsula and all other occupied territories.

The explosions, which killed one person and wounded 14, sent tourists fleeing in panic as plumes of smoke rose over the coastline nearby. Video showed shattered windows and holes in the brickwork of some buildings.

One tourist, Natalia Lipovaya, said that, “The earth was gone from under my feet” after the powerful blasts. “I was so scared,” she said.

Sergey Milochinsky, a local resident, recalled hearing a roar and seeing a mushroom cloud from his window. “Everything began to fall around, collapse,” he said.

Crimea’s regional leader, Sergei Aksyonov, said some 250 residents were moved to temporary housing after dozens of apartment buildings were damaged.

Russian authorities sought to downplay the explosions, saying Wednesday that all hotels and beaches were unaffected on the peninsula, which is a popular tourist destination for many Russians. But video posted on social media showed long lines of slowly moving cars on the road to Russia as tourists headed for home.

A Ukrainian presidential adviser, Oleksiy Arestovych, cryptically said that the blasts were either caused by Ukrainian-made long-range weapons or the work of Ukrainian guerrillas operating in Crimea.

A Ukrainian parliament member, Oleksandr Zavitnevich, said the airfield was rendered unusable. He reported on Facebook that it housed fighter jets, tactical reconnaissance aircraft and military transport planes.

Satellite images from Planet Labs PBC taken at midafternoon Wednesday showed some .75 square miles of grassland burned at the Saki base. Several craters marked the ground near the tarmac — typically the sign of a powerful explosion. The two runways bore no apparent damage and appeared to still be operational. Some of the fighter jets on the flight line had been moved farther down the runway, compared to images taken Tuesday before the blast.

The base has been home to the Russian 43rd Independent Naval Assault Air Squadron since Moscow seized Crimea. The squadron flies Sukhoi Su-24s and Sukhoi Su-30s. The base also includes a number of earth-covered bunkers and hangars around its periphery — typically used to house munitions in case of a fire. None appeared damaged.

“Official Kyiv has kept mum about it, but unofficially the military acknowledges that it was a Ukrainian strike,” Ukrainian military analyst Oleh Zhdanov said.

The base is about 125 miles from the closest Ukrainian position. Zhdanov suggested that Ukrainian forces could have struck it with Ukrainian or Western-supplied anti-ship missiles that have the necessary range.

The Washington-based Institute for the Study of War said it couldn’t independently determine what caused the explosions but noted that simultaneous blasts in two places at the base probably rule out an accidental fire but not sabotage or a missile attack.

It added: “The Kremlin has little incentive to accuse Ukraine of conducting strikes that caused the damage since such strikes would demonstrate the ineffectiveness of Russian air defense systems.”

During the war, the Kremlin has reported numerous fires and explosions on Russian territory near the Ukrainian border, blaming some of them on Ukrainian strikes. Ukrainian authorities have mostly kept silent about the incidents, preferring to keep the world guessing.

Neither side has released much information about their own casualties. In his nightly video address Wednesday, Ukrainian President Volodymyr Zelenskyy claimed nearly 43,000 Russian soldiers had been killed.

Colin Kahl, U.S. undersecretary of defense for policy, estimated Monday that Russian forces have sustained up to 80,000 deaths and injuries in the fighting. He did not break down the figure with an estimate of forces killed or provide a Ukrainian casualty count.

In other developments, Russian forces shelled areas across Ukraine on Tuesday night into Wednesday, including the central region of Dnipropetrovsk, where 13 people were killed, according to the region’s governor, Valentyn Reznichenko.

Reznichenko said the Russians fired at the city of Marganets and a nearby village. Dozens of residential buildings, two schools and several administrative buildings were damaged.

“It was a terrible night,” Reznichenko said. “It’s very hard to take bodies from under debris. We are facing a cruel enemy who engages in daily terror against our cities and villages.”

In Ukraine’s east, where fighting has raged for eight years, a Russian attack on the center of the city of Bakhmut in the Donetsk region killed seven, wounded six and damaged stores, homes and apartment buildings, setting off fires, Ukraine’s prosecutor general said on Telegram. Bakhmut is a key target for Russian forces as they advance on regional hubs.

In the city of Donetsk, which has been under the control of Russia-backed separatists since 2014, Ukrainian shelling hit a brewery, killing one person and wounding two, the separatists’ emergency service said. It said the shelling late Wednesday caused a leak of toxic ammonia and warned people to stay inside and breathe through cotton gauze.

Two residents of the village of Staryi Saltiv in the Kharkiv region in the northeast were killed Wednesday in Russian shelling, police reported.

In the country’s southeast, Moscow’s forces continued shelling the city of Nikopol across the Dnieper River from the Russian-occupied Zaporizhzhia power station, the biggest nuclear plant in Europe. Ukraine and Russia have accused each other of shelling it, stoking international fears of a catastrophe.

On Wednesday, foreign ministers of the Group of Seven industrialized democracies demanded that Russia immediately hand back full control of the plant to Ukraine. They said they are “profoundly concerned” about the risk of a nuclear accident with far-reaching consequences.

The U.N. Security Council scheduled an open meeting Thursday at Russia’s request on what it claims were Ukrainian attacks on the Zaporizhzhia plant. Rafael Grossi, the International Atomic Energy Agency chief who said last week that the situation at the plant “is completely out of control,” was expected to brief the council.