The Ukrainian Defense Ministry's Main Intelligence Directorate (HUR) has confirmed that an aviation training center in Russia's southwestern Voronezh region was struck in a drone attack early on April 9.
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"We will not disclose the details, but according to preliminary information, the main production facilities of the enterprise were damaged," HUR representative Andriy Yusov told RFE/RL.
Russian Telegram channels led by Baza, which is linked to Russia's security services, reported drone strikes on the premises of the aviation training center in Borisoglebsk, a city in the Voronezh region located some 255 kilometers northeast of the Ukrainian border.
The Ukrainian claim could not be independently verified.
The Russian Defense Ministry separately reported that four Ukrainian drones were allegedly shot down by its air-defense systems -- two in the Belgorod region and two in the Voronezh region. It said the drones did not cause any damage.
Ukraine, whose cities have been suffering massive casualties and material damage from Russian missile and drone strikes since the start of Moscow's invasion in February 2022, has in recent months stepped up its own strikes deep into Russian territory and off its shores.
Ukraine has targeted in particular Russian oil-production facilities with aerial drone strikes and military vessels with naval drones.
In an apparent confirmation that Ukrainian strikes have been effective, Reuters reported, citing anonymous sources, that Russia had asked Kazakhstan to supply it with 100,000 tons of gasoline.
The Istories website said Ukrainian drones might have destroyed 15 percent of Russia's oil refinery facilities, while the Russian statistics service said that by the end of last month, the country's gasoline production had decreased by 14.3 percent.
On April 8, Ukraine's military intelligence reportedly carried out a special operation that damaged a Russian warship docked off the exclave of Kaliningrad on the Baltic Sea in what appears to be the latest in a string of strikes on Russian ships.
In a video posted on X, Ukraine’s military intelligence said a fire inside the Serpukhov missile corvette had completely destroyed its means of communications and automation.
It gave no information about who started the fire and how or whether anyone was injured. Experts said the video appeared to indicate sabotage from inside the ship.
The Kyiv Post and Kyiv Independent both reported that Ukraine was behind the attack, citing unidentified intelligence sources.
Last month, the HUR said high-tech Ukrainian sea drones struck and "sunk" the Russian patrol vessel Sergey Kotov off the coast of occupied Crimea.
In February, Ukraine's military said it had destroyed the Tsezar Kunikov, one of the largest Russian landing ships, also off the Crimean coast, and had sunk the missile-armed corvette Ivanovets in the Black Sea using naval drones.
Russia has not commented on the Ukrainian claims.
Meanwhile, International Atomic Energy Agency (IAEA) chief Rafael Grossi said the UN body had been informed of a drone attack on a training center at the site of the Russian-held Zaporizhzhya nuclear power plant in Ukraine on April 9.
"Reported explosion consistent with IAEA team's observations. No direct threat to nuclear safety this time but latest incident again underlines extremely serious situation," he said on X, formerly Twitter.
The agency's board of governors has reportedly called an extraordinary meeting for April 11 to discuss attacks on the plant. In a confidential note to member states on April 9, the board's chairman said Ukraine and Russia had written to him on April 8 requesting the meeting.
Meanwhile, UN monitors recorded a sharp increase in civilian casualties in Ukraine last month as Russian forces stepped up attacks, the UN Human Rights Office said on April 9.
The UN Human Rights Monitoring Mission verified at least 604 civilians killed or injured in Ukraine in March, a 20 percent increase from February. The toll included at least 57 children, double the number from February.
The mission found that most civilian casualties -- 93.5 percent -- as well as most damage to educational and health facilities and critical infrastructure occurred in areas controlled by Ukraine.