KYIV, Ukraine--Explosions and fires ripped through an ammunition depot in Russian-occupied Crimea on Tuesday in the second suspected Ukrainian attack on the peninsula in just over a week, forcing the evacuation of more than 3,000 people.

Russia blamed the blasts in the village of Mayskoye on an “act of sabotage,” without naming the perpetrators.

Separately, the Russian business newspaper Kommersant quoted residents as saying plumes of black smoke also rose over an air base in Crimea’s Gvardeyskoye.

Ukraine stopped short of publicly claiming responsibility for any of the blasts, including those that destroyed nine Russian planes at another Crimean air base last week. Russia seized the Crimean Peninsula in 2014 and has used it to launch attacks against Ukraine in the war that began nearly six months ago.

If Ukrainian forces were behind the explosions, that would represent a significant escalation in the war. Such attacks could also indicate that Ukrainian operatives are able to penetrate deeply into Russian-occupied territory.

Ukrainian President Volodymyr Zelenskyy alluded to Ukrainian attacks behind enemy lines when he included individuals “who oppose the occupiers in their rear” in a list of people he thanked for supporting the country’s war effort.

In a video address Tuesday night, he also warned people not go near Russian military installations and storage sites for ammunition and equipment.

In another reported act of sabotage, Russia’s Tass news service quoted the FSB security agency as saying Ukrainian operatives blew up six high-voltage transmission towers earlier this month in Russia’s Kursk region, close to Ukraine.

The Kremlin has demanded that Kyiv recognize Crimea as part of Russia as a condition for ending the fighting, while Ukraine has vowed to drive Moscow’s forces from the peninsula on the Black Sea.

Videos posted on social media showed thick columns of smoke rising over raging flames in Mayskoye, and a series of explosions could be heard. The Russian Defense Ministry said a power plant, electrical lines, railroad tracks and apartment buildings were damaged.

“We came out to take a look and saw clouds of smoke coming from the cowshed where the military warehouses are,” said resident Maksim Moldovskiy. “We stayed there until about 7-8 a.m. Everything was exploding--flashes, fragments, debris falling on us. Then the emergency guys came and said they were evacuating everybody.”

Crimea’s regional leader, Sergei Aksyonov, said two people were injured and more than 3,000 evacuated from two villages.

“The detonations are rather strong. Ammunition is strewn all over the ground,” he said, adding that several homes burned down.

In what may have been retaliation for the attacks in Crimea, Russian warplanes fired missiles at a military airfield in Zhytomyr, 140 kilometers west of Kyiv, damaging a runway and vehicles, Ukrainian officials reported.

Crimea is a popular summer destination for Russian tourists, and last week’s explosions at Crimea’s Saki air base sent sunbathers on beaches fleeing as flames and pillars of smoke rose over the horizon.

Ukrainian officials warned Tuesday that Crimea would not be spared the ravages of war.

Rather than a travel destination, “Crimea occupied by Russians is about warehouse explosions and a high risk of death for invaders and thieves,” Ukrainian presidential adviser Mykhailo Podolyak said on Twitter.

Russia blamed last week’s explosions on an accidental detonation of munitions, but satellite photos and other evidence--including the dispersed blast sites--pointed to a Ukrainian attack, perhaps with anti-ship missiles, military analysts said.

Britain’s Defense Ministry said in an intelligence update that vessels in Russia’s Black Sea Fleet are in an “extremely defensive posture” in the waters off Crimea, with ships barely venturing out of sight of the coastline. Russia’s flagship Moskva went down in the Black Sea in April, and last month Ukrainian forces retook strategic Snake Island.

The Russian fleet’s “limited effectiveness undermines Russia’s overall invasion strategy,” the British said. “This means Ukraine can divert resources to press Russian ground forces elsewhere.”

Russian Defense Minister Sergei Shoigu charged that in addition to supplying arms to Ukraine, Western allies have provided detailed intelligence and instructors to help Ukraine operate weapons that can hit deep in occupied territory.

“Western intelligence agencies not only have provided target coordinates for launching strikes, but Western specialists also have overseen the input of those data into weapons systems,” Shoigu said.