Russia’s military captured a British national fighting with Ukrainian troops who have occupied part of Russia’s Kursk region, according to reports Monday, as Moscow began daylight drone attacks on civilian areas of Ukraine and its ground forces accelerated gains along parts of the front line.

The Briton was identified by state news agency Tass and other media as James Scott Rhys Anderson. Tass quoted him as saying that he had served as a signalman in the British army for four years and then joined the International Legion of Ukraine, formed early on in Russia’s nearly 3-year-old war against its neighbor.

On the battlefield, Ukrainian forces are straining to hold at bay a push by Russia’s bigger army at places in the eastern Donetsk region. Russian forces recently have gained ground at “a significantly quicker rate” than they did in the whole of last year, according to the Institute for the Study of War, a Washington think tank.

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The Russians have detected and are exploiting weaknesses in the Ukrainian defenses, it said in an analysis late Sunday.

The war surpassed 1,000 days last week, and the milestone coincided with a significant escalation in hostilities.

Meanwhile, Ukraine’s air force said Russia is adapting its drone tactics, as it fired 145 Shahed drones at Ukraine.

Russia has started launching drones during the day, whereas in the past most drone attacks occurred during the night, the air force said.

Andrii Kovalenko, the head of the National Security Council’s Counter-disinformation Center, said earlier this month that the Russians were looking to conserve their stocks of more destructive but more expensive missiles and also terrorize civilians.

The air force said it stopped almost all the drones before they struck.

But a morning missile attack on downtown Kharkiv, Ukraine’s second-largest city in the northeast, injured at least 23 people, according to Mayor Ihor Terekhov. He said the attack on a densely populated residential area was carried out by a modified surface-to-air S-400 missile.

A Russian ballistic missile also struck the southern Ukraine city of Odesa in the middle of the day, injuring 10 people as it landed in the downtown area, officials said.

Ukraine, meantime, continued its attacks on logistical targets inside Russia that support the Kremlin’s war effort.

Ukrainian drones set off explosions and a fire at an oil depot in Russia’s Kaluga region overnight, about 200 kilometers (120 miles) from the border, a military intelligence official told The Associated Press on condition of anonymity because the rules of his job do not allow him to be quoted by name.

Russia made no comment about the alleged strike. It was not possible to independently verify Ukraine’s claim.

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The Father of the British Man Says He Was Told by a Ukrainian Commander of His Capture

The captured Briton reportedly served as an instructor for Ukrainian troops and was deployed to the Kursk region against his will. Tass published a video of the man saying in English that he doesn’t want to be “here.”

The report couldn’t be independently verified, but if confirmed it could be one of the first publicly known case of a Western national captured on Russian soil while fighting for Ukraine.

The U.K. Embassy in Moscow said officials were “supporting the family of a British man following reports of his detention” but provided no further details.

The Russian Defense Ministry did not immediately respond to requests for comment.

The soldier’s father, Scott Anderson, told Britain’s Daily Mail newspaper that his son’s Ukrainian commander had informed him that the young man had been captured.

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Scott Anderson said his son had served in the British military for four years, then briefly worked as a police custody officer before going to Ukraine to fight. He said he tried to convince his son not to join the Ukrainian military, and now he fears for his safety.

“I’m hoping he’ll be used as a bargaining chip, but my son told me they torture their prisoners and I’m so frightened he’ll be tortured,” he told the newspaper.

The International Legion for Defense of Ukraine was created at the request of Ukrainian President Volodymyr Zelenskyy shortly after Russia’s full-scale invasion in February 2022.

The Legion is a unit of Ukraine’s Ground Forces that consists mostly of foreign volunteers. Apart from the Legion, Ukraine recruits foreigners to other units of its army, filling squads, companies, or even battalions.

Early on in the war, Ukraine’s authorities said over 20,000 people from 52 countries came to Ukraine to help it defend itself against Russia’s aggression. Ever since, the numbers of foreign fighters in the ranks of the Ukrainian military have been classified.