Russia said its emergency warnings app came under a "massive cyberattack" on Monday, hours after Ukraine reported a hack in an apparent exchange of blows between the foes, as their longest truce came to an end. Moscow's emergency ministry said hackers posted "false information" on the app, which is designed to warn the public of incoming drone attacks and other threats. Hours earlier, Ukraine said it suspected its air raid alert system had been compromised, after baseless alerts of a radiation threat appeared on the app. The cyberattacks came as the longest truce of the war, limited to Ukraine's eastern Kherson region, ended on Sunday after Russia refused the offer of an extension, according to Kyiv. Moscow did not immediately say who was behind the attack on its app, while Ukraine's Centre for Strategic Communications SPRAVDI blamed the hack it suffered on Russia. Read: Russian strikes cut power to thousands in Ukraine as drones damage Russian facility The rare pause in fighting, brokered by US First Lady Melania Trump and which began early Tuesday, had enabled a humanitarian mission to the Russian-occupied city of Oleshky as the war grinds through its fifth year. "The ceasefire, which was in effect from October 27 to November 1, has ended," Ukraine's Parliament Commissioner for Human Rights, Dmytro Lubinets, said. He called the temporary truce "an important step in our joint humanitarian efforts" with Russia. US-mediated talks between Russia and Ukraine are set to resume this month, having been effectively frozen since the United States and Israel launched joint strikes on Iran in February. Ukrainian President Volodymyr Zelensky said on Sunday his country would stop hitting Russian oil refineries – as US counterpart Donald Trump has demanded – if Washington provided Kyiv with powerful Patriot interceptor missiles. Raid alert app hack Kherson regional governor Oleksandr Prokudin warned local people to be particularly vigilant when the ceasefire ended and to "respond immediately to warnings about Russian attacks". "The Air Alarm application has probably been subjected to hostile interference," Ukraine's air force said in a message. "There is no radiation threat." Air force spokesperson Yuriy Ignat confirmed to AFP that the app had been hacked. Hours later, Russia's emergency ministry said its teams were working to fix a "massive cyberattack" which was "enabling attackers to send false information to the public". 'Worse than before' Russia's full-scale invasion in February 2022 has destroyed parts of eastern and southern Ukraine, left hundreds of thousands of soldiers and civilians dead and forced millions to flee their homes. AFP spoke to several Kherson residents, one of whom said the ceasefire had been a "breath of fresh air". "We have to use this time to get things done," said Volodymyr Omeltchenko, a 38-year-old gardener, before the truce ended. "We're pruning the rose bushes for winter." Read More: US approves $2.1 billion Patriot missile sale to Ukraine Pope Leo, who had pressed Russia for a truce in Oleshky, had said he hoped the temporary pause would "strengthen the desire for dialogue and lead to new concrete peace initiatives". A Ukrainian military officer, speaking on condition of anonymity, expressed concern that the fighting would be "worse than before" when it resumed. Russian forces on the other side of the Dnipro River had taken advantage of the calm of the past few days to amass new troops, transport ammunition stocks and collect intelligence on Ukrainian positions using surveillance drones, the officer said. Oil attacks Russia and Ukraine exchanged strikes elsewhere on Sunday. Russia said a drone had struck an "industrial enterprise" east of Moscow overnight, with Ukrainian media reporting that Kyiv had attacked the Kstovo oil refinery. Kyiv has repeatedly struck Russian oil and gas sites, in what it says is fair retaliation for Russian attacks on Ukrainian energy infrastructure. Trump has been pressing Kyiv to stop the attacks, blaming them for rising diesel costs that analysts attribute to the Iran war. Zelensky said on Fox News on Sunday that he told Trump and his team: "If you want us not to attack Russia's refineries, they have not to attack our energy system." "Another alternative, give us Patriot missiles," he said. Ukraine's energy ministry reported fresh power outages across the country Sunday, including in Kyiv, following Russian strikes on Ukrainian energy infrastructure.