Ukrainian forces entered the eastern Russian stronghold of Lyman on Saturday after encircling thousands of Russian troops, Kiev has said. Moscow has confirmed that its forces have left the town. The state-owned RIA Novosti agency quoted the Russian Defense Ministry as saying that "due to the threat of encirclement", Russian soldiers had "retreated to more advantageous lines". The capture of Lyman, a bastion that is critical for Moscow, would be a major setback for Moscow after President Vladimir Putin proclaimed the annexation of the Donetsk region — where Lyman is situated — along with three other regions on Friday. "We're already in Lyman, but there are battles," Serhii Cherevatyi, spokesperson for Ukraine's eastern forces, said. Two grinning Ukrainian soldiers taped the yellow-and-blue national flag on to the "Lyman" welcome sign at the town's entrance in Donetsk region's north, a video posted by the president's chief of staff showed. "Oct. 1. We're unfurling our state flag and establishing it on our land. Lyman will be Ukraine," one of the soldiers said, standing on the bonnet of a military vehicle. Ukraine's Defense Ministry said on Twitter that its air assault forces were entering Lyman. Earlier on Saturday, a Ukrainian military spokesperson said that Ukraine had encircled thousands of Russian troops at Lyman, which Russia has used as a logistics and transport hub for its operations in the north of the Donetsk region. "Lyman is important because it is the next step towards the liberation of the Ukrainian Donbas. It is an opportunity to go further to Kreminna and Sievierodonetsk, and it is psychologically very important," Cherevatyi said. Russia's forces at Lyman totaled around 5,000 to 5,500 soldiers, but the number of encircled troops may have fallen because of casualties and some soldiers trying to break out of the encirclement, he added. A few hours earlier, US military analysts forecast that Ukraine would likely retake the key Russian-occupied town in the country's east in the next three days. "Russian forces continued to withdraw from positions around Lyman on Sept. 30 as Ukrainian forces continued to envelop Russian troops in the area," the Institute for the Study of War, a Washington-based think tank, said in its latest assessment of the war. Ukrainian officials said on Friday that their troops have captured two villages that lie very close to Lyman, in the clearest sign yet the town could soon fall. Ukraine also is making "incremental" gains around Kupiansk and the eastern bank of the Oskil River, which became a key front line since the Ukrainian counteroffensive regained control of the Kharkiv region in September. Meanwhile, Turkey's Foreign Ministry said on Saturday it rejects Russia's annexation of four regions in Ukraine, adding the decision is a "grave violation" of international law. Turkey, a NATO member, has conducted a diplomatic balancing act since Russia invaded Ukraine on Feb. 24. Ankara opposes Western sanctions on Russia and has close ties with both Moscow and Kirv, its Black Sea neighbors. It has also criticized Russia's invasion and sent armed drones to Ukraine. The Turkish ministry said on Saturday it had not recognized Russia's annexation of Crimea in 2014, adding that it rejects Russia's decision to annex the four regions, Donetsk, Luhansk, Kherson and Zaporizhzhia. "This decision, which constitutes a grave violation of the established principles of international law, cannot be accepted," the ministry said. "We reiterate our support to the resolution of this war, the severity of which keeps growing, based on a just peace that will be reached through negotiations," it added. Russian President Vladimir Putin proclaimed the annexation of the regions on Friday, after Russia held what it called referendums in occupied areas of Ukraine. Western governments and Kiev said the votes breached international law and were coercive and non-representative. Meanwhile, Ukraine's nuclear power provider has accused Russia of "kidnapping" the head of the Russian-occupied Zaporizhzhia plant. The head of Energoatom, the state-owned company in charge of the plant, said on Saturday that Ihor Murashov was detained on his way from Europe's largest nuclear plant to the town of Enerhodar around 16.00 local time (1500 CET) on Friday. "He was taken out of the car, and with his eyes blindfolded he was driven in an unknown direction," Petro Kotin wrote on the Telegram messaging app, adding there was no immediate word on Murashov's fate. "His detention by (Russia) jeopardizes the safety of Ukraine and Europe's largest nuclear power plant," Kotin added, calling for Murashov's immediate release. The United Nations nuclear watchdog later said Russia had confirmed the move. The IAEA said it had been informed by Russian authorities that Murashov was being held for questioning. Moscow, however, has not publicly commented. The Zaporizhzhia plant has been a focal point of Russia's seven-month invasion of Ukraine, as Moscow and Kiev accuse each other of shelling the facility, risking a nuclear disaster. Ukrainian technicians continued running it after Russian troops seized the power station. The plant's last reactor was shut down in September amid ongoing shelling near the facility. Also Russian forces were almost certainly responsible for a deadly missile strike on a convoy southeast of Zaporizhzhia on Friday in which at least 25 civilians were reportedly killed, the British Defense Ministry said in its latest intelligence update. The missile involved was probably "a Russian long-range air defense missile being used in a ground attack role", the MoD report says. It added that Russia's stock of such missiles is likely limited and its use in a ground attack role has likely been "driven by overall munitions shortages". On Vladimir Putin's illegal annexation of four Ukrainian regions announced on Friday, the ministry notes that "Russia is expending strategically valuable military assets in attempts to achieve tactical advantage and in the process is killing civilians it now claims are its own citizens". Ukraine's military claimed on Saturday that Russia would need to deploy cadets before they complete their training because of a lack of manpower in the war. Putin ordered a mass mobilization of Russian army reservists last week to supplement his troops in Ukraine, and thousands of men have fled the country to avoid the call-up. The Ukrainian military's general staff said cadets at the Tyumen Military School and at the Ryazan Airborne School would be sent to participate in Russia's mobilization. It offered no details on how it gathered the information, though Kyiv has electronically intercepted mobile phone calls from Russian soldiers amid the conflict. Moscow's annexation of four new occupied Ukrainian territories makes it "almost" impossible to end the war in Ukraine, EU diplomatic chief Josep Borrell said on Saturday. The annexation of the regions of Donetsk, Lugansk, Zaporizhzhia and Kherson, announced on Friday by Russian President Putin, makes it "much more difficult, impossible, almost impossible, to end the war," Borrell said on Spanish television channel RTVE. "Russia is losing" the war, "it has lost it in moral and political terms", but "Ukraine has not yet won", he said a little later at a forum at La Toja in the northeastern Galicia region, where he defended the European sanctions imposed on Moscow and military aid to Kiev, and called for perseverance in this direction. "We must do better than this" and "make the world aware of the reasons and consequences of this war", he pleaded, recalling that Brazil and India had refrained from condemning the Russian annexations at the UN Security Council. According to Josep Borrell, the Europeans have built "a garden" which is "surrounded by jungle". "If we do not want the jungle to invade the garden... we will have to get involved," he warned, calling on Europe to strengthen its military arsenal. "This is not a whim... it is necessary, indispensable for survival," he said. — Euronews