Russia will make changes to its doctrine on the use of nuclear weapons in response to what it regards as western escalation in the war in Ukraine, state media quoted deputy foreign minister Sergei Ryabkov as saying on Sunday. The existing nuclear doctrine, set out in a decree by President Vladimir Putin in 2020, says Russia may use nuclear weapons in the event of a nuclear attack by an enemy or a conventional attack that threatens the existence of the state. Some hawks among Russia’s military analysts have urged Putin to lower the threshold for nuclear use in order to “sober up” Russia’s enemies in the west. Ryabkov’s comments on Sunday were the clearest statement yet that changes would indeed be made. “The work is at an advanced stage, and there is a clear intent to make corrections,” state news agency Tass cited Ryabkov as saying. The decision was “connected with the escalation course of our western adversaries” in connection with the Ukraine conflict. Polish and allied aircraft were activated early on Monday to ensure the safety of Polish airspace after Russia launched air strikes on Ukraine, the Operational Command of the Polish armed forces said. “In the southeastern part of the country there may be an increased noise level related to the commencement of operations in our airspace by Polish and allied aircraft,” the command said on X. South-east Poland borders Ukraine. Ukraine carried out one of its biggest ever drone attacks on Russia overnight to Sunday, with videos showing a series of explosions and fires at power stations and refineries including in Moscow. Russia’s defence ministry played down the overnight strikes. It said it had intercepted and destroyed 158 unmanned enemy aerial vehicles. These were shot down over 15 regions, it claimed. Footage posted on Telegram channels suggested some of the long-range Ukrainian drones damaged targets deep inside Russia. At least one struck an oil refinery in the Kapotnya district in south-east Moscow. More drones hit a thermal power station in the Tver region, north of Moscow. There was an explosion at the Konakovo station, one of the biggest in Russia. An orange fireball engulfed several transformers. In eastern Ukraine, where the heaviest fighting of the war is concentrated, Russian forces continued to advance towards Pokrovsk, which is a vital military hub and transport link to towns and cities further north. Russia’s defence ministry said on Sunday its forces had captured two more settlements in Donetsk region and were “continuing to advance deep into the enemy defences”. One of them, Ptyche, is just 21km (13 miles) southeast of Pokrovsk. At least three people were killed and nine wounded in Russian shelling of Kurakhove, a town around 35 km south of Pokrovsk, Ukrainian officials said. At least 47 people, including five children, were injured on Sunday after Russian missiles struck a shopping mall and events complex in Ukraine‘s northeastern city of Kharkiv, officials said. The attack prompted Ukrainian President Volodymyr Zelenskiy to renew calls on allies to allow Kyiv to fire western-supplied missiles deeper into enemy territory and reduce the military threat posed by Russia. A Ukrainian helicopter on a military training flight crashed on Sunday, killing its two-member crew, the Air Force’s university said. The Kharkiv Air Force University in a post on Facebook said investigators and officials from Ukraine’s defence ministry were working to determine the cause of the crash. No further details were immediately available. Ukrainian forces shelled Russia’s southern Belgorod region on Sunday, injuring 11 people, including two children who were seriously hurt, regional governor Vyacheslav Gladkov said. Gladkov, writing on the Telegram messaging app, said the two boys were undergoing surgery after sustaining serious injuries, including one with extensive wounds on both legs.