Vladimir Putin has declared martial law in the four provinces of Ukraine where Moscow controls territory after Russian officials warned of a Ukrainian assault on the key southern city of Kherson. “We are working on solving very complex, large-scale tasks to ensure a reliable future for Russia, the future of our people,” the Russian president said in televised remarks to members of his security council. The law, published on the Kremlin website, gives far-reaching emergency powers to the Russian-installed heads of Luhansk, Donetsk, Zaporizhzhia and Kherson provinces, which Russia recently proclaimed as annexed after sham referendums. Law enforcement agencies have been given three days to submit specific proposals. The Kremlin decree also puts Russia on a stronger economic war footing. Putin ordered an “economic mobilisation” in six provinces that border Ukraine, plus Crimea and Sevastopol, which Russian illegally annexed in 2014. He said he was granting additional authority to the leaders of all Russian provinces to maintain public order and increase production in support of Moscow’s war, which is entering its eighth month. The law also limits the freedom to move in and out of the eight provinces. Shortly after the Russian president’s statements, his spokesperson, Dmitry Peskov, said Russia was not planning on closing its international borders. Earlier in the day, the head of the occupying administration in Kherson spoke of plans to move up to 60,000 people across the Dnieper River and into Russia as Moscow attempted to cling to the city before a Ukrainian counteroffensive. Vladimir Saldo said Russia would transport 50,000-60,000 people to the Dnieper’s east bank – and then to Russia – at a rate of 10,000 people each day. “We are not going to surrender the city,” he said in a nationally televised interview on Wednesday. Yet the mass removal of civilians would set the stage for just that. Kherson, the second-largest population centre in Ukraine captured by Russia during the war, is on the Dnieper’s west bank. Officials said the plan was to remove civilians and the occupying authorities from the city. People would not be allowed to enter Kherson province for seven days, they added. Residents are under pressure to leave. A number have reported receiving mass text messages warning the city would be shelled and informing them that buses would be leaving from the port from 7am. Workers such as teachers and doctors were also being told to leave. “I am not planning to go anywhere,” one local resident, Svetlana, said. “They are trying to sow panic but we aren’t buying it. I don’t believe Ukraine is going to bomb us. We are staying put.” A Ukrainian official, Yaroslav Yanushevich, the head of the Kherson regional military administration, told people not to comply with the evacuation request. “People of Kherson, I urge you to ignore everything the occupiers tell you or demand from you. They want to take our people hostage and use them as human shields. Do not allow the evil empire to hide behind you, your parents, your children,” he said in a post on his Telegram channel. “Ukrainian army does not destroy Ukrainian cities and villages.” Another Ukrainian official compared the announced evacuation of civilians to “deportations as in Soviet times”. “Its purpose is to create a kind of panic in Kherson and a propaganda picture,” Sergiy Khlan, a deputy head of the Kherson region, said. Russian television footage showed hundreds of people gathered at the port on Wednesday morning waiting to be removed. Russian officials have promised to help them buy property in mainland Russia, suggesting they were not planning for a return of civilians to the city in the foreseeable future. Russia’s army would remain in Kherson, its leadership said, although the head of its invasion force, Gen Sergei Surovikin, hinted in an interview that his forces may be forced to retreat. “I repeat: [the situation] is already very difficult today,” he said. “We will act consciously, in a timely manner. I do not exclude the adoption of the most difficult decisions.” Saldo said the movement of civilians would be tied to a decision “to build sizeable defensive fortifications to repulse any attack”. “There is no place for civilians where the military is operating,” he wrote. “Let the Russian army fulfil its task.” Russian forces appeared to have resumed aerial attacks on Kyiv on Wednesday, with local people reporting explosions from anti-air defence systems in the skies over the Ukrainian capital. Occupation officials have warned of a coming Ukrainian counteroffensive in the area. “The battle for Kherson will begin in the very near future,” said Kirill Stremousov, the Russian-installed deputy administrator in Kherson. “The civilian population is advised, if possible, to leave the area of the upcoming fierce hostilities.” The warnings are an attempt to avoid a repeat of the situation in Kharkiv province, where the Russian military was criticised for its chaotic retreat, in many cases leaving behind local Ukrainians who had collaborated with the occupation governments. Kherson is the capital of one of the four provinces Russia claimed to annex amid much fanfare after sham referendums last month. Since then Ukraine’s advance has meant none of the provinces are under full Russian control. A Ukrainian presidential adviser noted that only a month after the “pompous announcement of Kherson annexation” the city was being “ceremoniously evacuated in anticipation of [Ukrainian] justice”. “Reality can hurt if you live in a fictional fantasy world,” wrote Mykhailo Podolyak. Ben Wallace, the UK defence secretary, rushed to Washington at short notice on Tuesday for urgent consultations, prompting conjecture he was having discussions about nuclear threats made by Russia. The UK government previously said it had seen no suspicious activity that might be a precursor to the deployment of a tactical nuclear weapon. A UK defence source sought to quell the speculation, saying the purpose of the meeting was to discuss the state of the war more generally. “As we approach winter in Ukraine, with their successes on the battleground against Russian forces, and in light of Putin’s recent actions, it was important to meet face to face with US Secretary of Defense Lloyd Austin and others from the US Administration to discuss our shared security concerns,” they said. US defence officials said this week they had been given no official Russian notification of a plan to start Russia’s annual nuclear training exercise, codenamed Grom. The lack of the normal high-level military-to-military contact places extra pressure on western intelligence to distinguish a training exercise from a real threat. Wallace is thought to be discussing how to prevent Iranian missiles and drones reaching Russia with new air defence systems, as well as the likely location from which they are being dispatched.