KYIV: Russian and Ukrainian forces exchanged missile and artillery barrages that killed at least six people Thursday as both sides refused to concede any ground despite recent military setbacks for Moscow and the toll on the invaded country after almost seven months of war.Russian missile strikes in the southern city of Zaporizhzhia left one person dead and five others wounded, Ukrainian officials said. Officials in the separatist-controlled city of Donetsk said Ukrainian shelling killed at least five people.Demonstrating that neither side was ready to ease up or pause the fighting, the exchange of fire came hours after the two sides made a major prisoner swap and the day after Russian President Vladimir Putin called up reserve troops to supplement his forces.Kyrylo Tymoshenko, the deputy of the Ukrainian president’s office, said a hotel in the central part of Zaporizhzhia, said a hotel in the center of the city was struck and rescuers were trying to free people trapped in the rubble.The governor of the Zaporizhzhia region, Oleksandr Starukh said Russian forces targeted infrastructure facilities and also damaged nearby apartment buildings. The region is one of four where officials installed by Moscow plan to hold referendums starting Friday on becoming part of Russia, but the city itself is in Ukrainian hands.Meanwhile, the mayor of the separatist-controlled city of Donetsk, Alexei Kulemzin, said at least five people where killed when Ukrainian shelling Thursday hit a covered market and a passenger minibus.Just hours before Thursday’s attacks, a high-profile prisoner swap saw 215 Ukrainian and foreign fighters exchanged — 200 of them for a single person, an ally of Putin’s. Kremlin spokesman Dmitry Peskov wouldn’t confirm if the lone Putin ally — pro-Russian Ukrainian opposition leader Viktor Medvedchuk — was part of the swap.Among the freed fighters were Ukrainian defenders of a steel plant in Mariupol during a long Russian siege and 10 foreigners, including five British nationals and two US military veterans, who had fought with Ukrainian forces.A video on the BBC news website Thursday showed two of the released British men, Aiden Aslin and Shaun Pinner, speaking inside a plane. It said they had arrived in Riyadh, Saudi Arabia.”We just want to let everyone know that we’re now out of the danger zone and we’re on our way home to our families,” Aslin said in the video, as Pinner added: “By the skin of our teeth.”The speed with which the Russian missile attack came after the swap suggested that the Kremlin was seeking to dispel any notion of weakness or waning determination to achieve its war aims following recent battlefield losses and setbacks that gravely undercut the aura of Russian military might.Those losses culminated Wednesday in Putin’s order for a partial mobilization of reservists to bolster his forces in Ukraine. The order sparked rare protests in the Russia and was derided in the West as an act of weakness and desperation.The partial call-up was short on details, raising concerns of a wider draft that sent some Russians scrambling to buy plane tickets to flee the country.Peskov, the Kremlin spokesman, said the mobilization was needed because Russia was “de facto facing all of NATO,” a reference to the military aid and other support that alliance members have provided to Ukraine.A senior Kremlin official on Thursday repeated Putin’s threat to use nuclear weapons if Russian territory comes under attack.Dmitry Medvedev, deputy head of Russia’s Security Council, said on his messaging app channel Thursday that strategic nuclear weapons are one of the options to safeguard Russian-controlled territories in eastern and southern Ukraine. The remark appeared to serve as a warning that Moscow could also target Ukraine’s Western allies.Pro-Moscow authorities in Ukraine’s Russian-controlled regions are preparing to hold referendums on becoming part of Russia — a move that could allow Moscow to escalate the war. The votes start Friday in the Luhansk, Kherson, Zaporizhzhia and Donetsk regions.Foreign leaders have called the votes illegitimate and nonbinding. Ukrainian President Volodymyr Zelensky said they were a “sham” and “noise” to distract the public.One person was killed during Russian shelling overnight in the center of Nikopol city, across the river from the Zaporizhzhia Nuclear Power Plant, according to Dnipropetrovsk region governor Valentyn Reznichenko.The office of Zelensky’s office said five people were killed by shelling in the Donetsk region over the past day.