Amid reports that General Valery Gerasimov, the commander of the Russian armed forces, had been killed in Ukraine, US officials said that while visiting Donbas last week, they could not confirm reports that he had been wounded. A senior US defense official said: “We can confirm that he was in Donbass. It is certainly possible that his journey was in some way a surveillance in an attempt to measure for himself what was happening. “What he learned, what he passed on to his commanders, if nothing else, we just do not know. He was in Donbass for several days last week. We do not believe he is still there.” It came as British intelligence officials said Russia had lost a quarter of its invading army to the failed occupation of Ukraine. Some of Moscow’s most select units, including its Air Force, suffered the highest levels of damage in the first 68 days of the conflict, and a quarter of the Russian forces used in the invasion were now “ineffective in battle.” The Kremlin has deployed more than 120 regular battalion groups, each from 600 to 1,000 troops, in Ukraine, which accounts for about 65 percent of Russia’s total ground combat force, according to the report. The Defense Ministry said that “it will probably take years for Russia to rebuild these forces.” On Sunday night, unconfirmed local reports from the southern port of Odessa reported that a 15-year-old boy was killed and a 17-year-old girl was injured in a Russian rocket attack. The rocket, which was apparently aimed at a military installation, also damaged a nearby monastery.