KYIV, Ukraine — Explosions hit Russian targets in and near occupied Crimea overnight into Wednesday, as Ukraine appeared to be intensifying attacks on Russian military strongholds before an expected counteroffensive.
In Crimea, drones struck a border guard post in Simferopol on Tuesday night, according to photos and video shared on social media and geolocated by Radio Liberty, a U.S. government-funded broadcaster. Ukraine did not directly claim responsibility for the incident, but Ukraine’s military intelligence spokesman, Andriy Chernyak, said in a statement on Wednesday morning: “Of course, the enemy must be cut off from Crimea.”
Crimea, the Ukrainian peninsula that Russia illegally annexed in 2014, has served as a key staging ground for Moscow’s full-scale invasion and a hub for the supply of troops and weapons to its occupying force in southern Ukraine.
Just east of Crimea, inside Russian territory in the village of Volna, the Russian authorities reported an explosion at a fuel depot after a drone attack before dawn on Wednesday. Videos showed dark smoke rising from a fire visible on the nearby bridge linking Crimea to Russia.
Russian state media reported that the fire was caused by a drone falling on the oil facility, in Russia’s Krasnodar region.
Ukrainian forces have attacked for months inside Crimea, but the assaults have increased in recent days as Kyiv carries out what its officials describe as the final stages of planning for a counteroffensive to take back seized territory.
U.S. officials say the Ukrainian military has been bolstered by training and equipment from Western allies. Gen. Mark Milley, the head of the Joint Chiefs of Staff, said that the United States and NATO allies have helped train and supply about nine Ukrainian brigades, including some light infantry units that are prepared to conduct both offensive and defensive operations.
“The Ukrainians right now have the capability to attack, they can conduct offensive operations, and they also have the capability to defend, significantly enhanced from what they were just a year ago for conventional operations,” General Milley told Foreign Affairs magazine in comments published on Tuesday.
While Ukraine has not disclosed detailed plans for a counteroffensive, military officials have described recent blasts in Crimea and other Russian-occupied areas as part of an effort to disrupt Russia’s logistical capacity. Over the weekend, a spokeswoman for Ukraine’s southern military command, Natalia Humeniuk, said that an attack on an oil depot in the Crimean port city of Sevastopol, the home of Russia’s Black Sea naval fleet, was part of preparations for “the broad, full-scale offensive that everyone expects.”
Separately, Russia’s top security agency said on Wednesday that it had arrested seven individuals who planned to conduct “high-profile sabotage and terrorist acts” in Crimea in cooperation with Ukrainian military intelligence. Among the targets were several Kremlin-installed officials including the governor of Crimea, Sergei Aksyonov, according to the agency, the Federal Security Service, or F.S.B., the successor to the K.G.B. It did not publicly release detailed evidence for its claims.
Across occupied areas, Ukraine’s military appears to be stepping up attacks. The Ukrainian Air Force said on Wednesday morning that over the past 24 hours it had carried out strikes on concentrations of Russian troops, ammunition depots, a Russian command post and other targets. The claims could not be independently verified.
Meanwhile, Ukrainian officials reported strikes from Russian aircraft, drones or artillery against cities and towns across the country.
In Kyiv, the capital, explosions echoed again overnight as air defense systems engaged Russian attack drones, with regional officials saying that all were shot down. A Russian aircraft also launched strikes at a village in the northeastern region of Sumy and drones targeted the Dnipro region of central Ukraine and Mykolaiv in the south, according to Ukrainian officials. There were no immediate reports of casualties in those incidents.
Ivan Nechepurenko contributed reporting.