Ukraine’s president has claimed Kyiv’s troops have full control over the Russian town of Sudzha, which had a prewar population of 5,000 people and contains infrastructure pumping Russian gas towards Europe. Sudzha, roughly six miles (9.6km) inside Russian territory, is the biggest of 80 settlements that Ukraine claims to have taken during the 10 days since its surprise incursion into Russia began. “General Syrskyi reported on the completion of the liberation of the town of Sudzha from the Russian military. A Ukrainian military commandant’s office is being established there now,” said Volodymyr Zelenskiy, after receiving a briefing from the commander in chief of Ukraine’s armed forces, Oleksandr Syrskyi, on Thursday. The claim could not be independently verified, but a Ukrainian television channel broadcast a report from Sudzha on Wednesday suggesting the town was under Ukrainian control. While some residents have remained, sheltering from the fighting in basements, most have been evacuated. “We hid in the bushes,” said one, Tatyana Anikeyeva, speaking to Russian television from a facility helping evacuees. “Volunteers were handing out water, food, bread to people on the go. The sound of the cannonade continued without any break. The house was shaking.” Sudzha hosts a measuring station for Russian natural gas arriving from western Siberia, which then flows through Ukrainian pipelines to Europe, accounting for about 3% of European gas imports. “Smart people in Kyiv have calculated that they should take over this hub, in order that the Russian army will have to destroy it [to take it back],” Andrei Fedorov, a former Russian deputy foreign minister, said on a state television talkshow. “This means deliveries of gas to Europe will be stopped, because of Russia’s actions, not Ukraine’s. By the way, this will hit Hungary and Slovakia very hard,” he added. So far there has been no indication of a disruption to the gas flow. Both Ukraine and Russia claimed advances elsewhere in Kursk region on Thursday. Russia’s defence ministry said its forces were continuing to “repel the attempted incursion of the Ukrainian armed forces” and had re-established control over the settlement of Krupets. At the same time, Kursk’s acting regional governor, Alexei Smirnov, ordered the evacuation of Glushkovo region, 28 miles north-west of Sudzha, suggesting a fear that Ukraine’s advance would continue. More than 120,000 residents of the region have already been evacuated, according to local authorities. Challenger 2 tanks donated to Ukraine by Britain have been used in active combat on Russian territory, Sky News reported on Thursday. The UK Ministry of Defence did not comment on the claim but said “operations inside Russia” were a permissible use of tanks and other arms provided to Ukraine. Kyiv has said part of the goal of the operation is to create a “buffer zone” that would stop Russian forces from attacking Ukraine, but it is not clear how much territory is involved, and for how long it will attempt to hold. Also on Thursday, Ukraine’s SBU security services released a video it claimed featured dozens of Russian troops who had surrendered and had been taken prisoner. “We have a new replenishment of our ‘exchange fund’,” said Zelenskiy, commenting on the new prisoners of war. Thousands of Ukrainians remain in Russian captivity and Kyiv hopes to rejuvenate a stalled process of prisoner exchanges. Ukraine’s human rights ombudsman, Dmytro Lubinets, said on Thursday he had had a “proactive conversation” with his Russian counterpart over the possibility of organising a new exchange. Many Russian officials have sought to play down the Ukrainian attack, the first time that parts of Russian territory have been occupied by a foreign army since the second world war. Vladimir Putin has avoided calling it an “invasion” or “incursion” and has instead announced an “anti-terrorist operation” in the area. Speaking at the United Nations on Wednesday, Russia’s deputy ambassador to the body, Dmitry Polyansky, called the Ukrainian assault on Kursk a “mad and reckless operation” and said Russia would soon restore control. “What’s happening in Kursk is the incursion of terrorist sabotage groups, so there is no frontline as such … There is an incursion because there are forests that are very difficult to control,” said Polyansky. The longer the Ukrainian advance continues, the harder it is to brush it off as a minor setback. On state television Fedorov offered rare criticism of official Russian messaging, bemoaning the “constant lies coming from our side about the weakness of the Ukrainian army”. He said it was time to admit that the Ukrainian advance was serious and would require a sustained effort to repel.