Powerful explosions erupted at a Russian air base in Ukraine’s Crimean Peninsula on Tuesday, killing one person and wounding five others, authorities said, but the cause of the blasts was unknown.

Witnesses reported hearing at least 12 blasts shortly after 3:15 p.m. local time Tuesday.

Russia’s Defense Ministry said “several aviation ammunition stores” blew up at the Saki base in the region seized by Russia in 2014, but it emphasized the installation had not been attacked and no aircraft had been damaged.

Ukraine denied responsibility.

“Of course not. What do we have to do with this,” Ukrainian presidential aide Mykhailo Podolyak said. A statement from Ukraine’s defense ministry said it “once again draws attention to fire safety rules.”

Shortly after the explosions there was widespread speculation on Ukrainian social networks that Kyiv’s forces had hit the base with long-range missiles. Sunbathers fled a nearby beach as huge clouds of smoke from the explosions rose over the horizon, while authorities sealed off the area around the base within a radius of five kilometers.

Rising smoke can be seen from the beach at Saky after explosions were heard from the direction of a Russian military airbase near Novofedorivka, Crimea, Aug. 9, 2022.

Rising smoke can be seen from the beach at Saky after explosions were heard from the direction of a Russian military airbase near Novofedorivka, Crimea, Aug. 9, 2022.

Ukraine’s forces have not attacked Crimea during Russia’s offensive, now in its sixth month, with officials in Moscow warning Ukraine that any attack on Crimea would trigger massive retaliation, including strikes on “decision-making centers” in Kyiv.

But a small-scale, makeshift drone hit the headquarters of Russia’s Black Sea Fleet in the Crimean port of Sevastopol last month, an attack blamed on Ukrainian saboteurs. The Saki base has been used by Russian warplanes to strike areas in Ukraine’s southern region.

In his nightly video address Tuesday, Ukrainian President Volodymyr Zelenskyy said people should focus on Crimea.

“The Black Sea region cannot be safe while Crimea is occupied,” he said, reiterating Kyiv’s position that Crimea must be returned to Ukraine.

Also Tuesday, the U.S. State Department approved $89 million to help equip and train 100 Ukraine teams to clear landmines and unexploded bombs, a U.S. official said, speaking on the condition of anonymity under ground rules set by the State Department.

British intelligence had warned Monday that Russia was using anti-personnel mines in an effort to defend and hold its defense lines in the eastern Donbas region, with resulting risks to both the military and local civilian populations.

The demining training will be done by contractors, specialists and nonprofits, the official said.

“By our estimates, 160,000 square kilometers of Ukrainian land need demining, which is about the size of Virginia, Maryland and Connecticut combined,” said Andriy Yermak, a top Zelenskyy aide.

People wait in a line to receive food at a humanitarian aid distribution point in Zaporizhzhia, Ukraine, Aug. 9, 2022.

People wait in a line to receive food at a humanitarian aid distribution point in Zaporizhzhia, Ukraine, Aug. 9, 2022.

Ukrainian officials said earlier Tuesday that in the last day at least three Ukrainian civilians were killed and 23 were wounded by Russian shelling, including an attack not far from the Russian-occupied Zaporizhzhia nuclear power plant.

Dnipropetrovsk Gov. Valentyn Reznichenko said Russian forces fired more than 120 rockets at the town of Nikopol, which is across the Dnieper River from the nuclear facility. Several apartment buildings and industrial sites were damaged, he said.

In recent days, Ukraine and Russia have accused each other of shelling the power station, the biggest nuclear plant in Europe, and officials have been worrying about a nuclear catastrophe.

Meanwhile, the Ukrainian Army’s General Staff said early Tuesday that a Russian offensive is continuing toward the hub cities of Bakhmut and Avdiyivka in the eastern Donetsk region as Moscow tries to inflict “maximum losses” on Ukrainian forces.

Ukraine said the Russian Air Force was bombarding military facilities in the direction of Donetsk in support of artillery and other ground operations aimed at dislodging Ukrainian units from the front lines.

But Kyiv’s military planners said their forces had repelled reconnaissance and offensive operations in a handful of settlements around Ivano-Daryivka, Bakhmut, and Zaitsevo.

They said Russian forces had withdrawn after unsuccessful pushes around Avdiyivka and Krasnohorivka.

Some information in this report came from the Associated Press and Reuters.