KYIV, Ukraine – Six and a half feet up a ladder inside a small shed at the back of Oleksandr Kadet’s house is an underground room with a cement hatch he hopes he never has to use .
For the past two weeks, Mr Kadet, 32, said he and his wife, who live outside the Ukrainian capital Kyiv, had been preparing for the possibility of a nuclear attack by storing the room – an old well they converted into a bunker – with bottled water, canned food, radios and power banks.
“We are more anxious now, especially after the attacks yesterday,” Kadet said on Tuesday, a day after a series of Russian missile attacks across Ukraine. “But we believe that in the event of a nuclear explosion, we will be able to survive if we stay in the shelter for a while.”
Escalation fears grew on Saturday after an attack on the 12-mile-long Kerch Strait bridge linking Russia to the Crimean Peninsula, which Moscow annexed in 2014. Ukrainians initially celebrated, but that quickly gave way to concern that such a brazen assault on a symbol of President Vladimir V. Putin’s reign could provoke severe retaliation.
Even before these recent events, however, concerns about the possibility of nuclear catastrophe had increasingly worked their way into Ukraine’s national psyche. The fear is that Russia could either use tactical nuclear weapons or launch a conventional attack on one of Ukraine’s nuclear power plants.
US officials have said they believe the chances of Russia using nuclear weapons are low, and senior US officials have said they have seen no evidence that Mr Putin is moving any of his nuclear assets .
On Sunday, Mr Putin called the assault on the bridge a “terrorist attack aimed at destroying the critically important civilian infrastructure of the Russian Federation”.
But his spokesman, Dmitry S. Peskov, appeared to allay fears of nuclear retaliation, saying the attack on the bridge fell outside the category of Russian defense doctrine that authorized such a response.
Last month, Mr Putin raised fears he could use nuclear weapons when he warned that he would “use all means at our disposal to protect Russia and our people”, if Russian-controlled territory was threatened.
“It’s not a bluff,” he said.
A few days later, Russia illegally annexed four Ukrainian territories.
Mr. Kadet, who noted that he started preparing two weeks ago, said it was best to have an action plan.
“It’s psychologically easier because you know you’re at least prepared one way or another,” he said. “It’s no guarantee it’ll save you, but at least you’re prepared.”
Kyiv residents said they had felt suspicious even before the latest missile strikes on Monday.
Immediately after the attack on the bridge, many Ukrainians shared their joy on social media. They clinked glasses triumphantly in bars across the capital over the weekend and posed for selfies in front of posters of the burning bridge.
But concern soon set in.
“I feel a real fear of how the Russians are going to respond to this,” said Krystina Gevorkova, 30, who was shopping with her friend in Kyiv on Sunday. “Before, we felt safer here,” she added. “Now I have a feeling something is going to happen.”
Kyiv was spared for months the worst of the Russian onslaught while Moscow instead focused its attention on southeastern Ukraine. But on Monday, a Russian missile struck a few blocks from where Ms Gevorkova had spoken.
She said she had read about how to stay safe during a nuclear war, but was skeptical about getting help.
“There’s really nothing we can do,” she said.
The war has felt far from Kyiv in recent months as the rhythms of life return to some semblance of normality after Russian forces were ousted from parts of northeastern Ukraine. Nevertheless, the city is also slowly preparing for a possible nuclear attack.
Kyiv City Council said on Friday that potassium iodide pills would be distributed to residents in the event of a nuclear accident “based on medical recommendations”, adding that the pills were also available at city pharmacies.
Potassium iodide is used to saturate a person’s thyroid with iodine so that radioactive iodine inhaled or ingested after exposure is not retained by the gland.
Alina Bozhedomova, 23, a pharmacist in Kyiv, said customers came daily to pick up the pills, but added: “I haven’t seen people freaking out about it.”
Some elementary schools have advised parents to prepare emergency kits for their children to keep with them at school.
Nadiia Stelmakh, 50, who works at a market selling household items, said a mother came to see her with a list from school that included latex gloves, a poncho, boot covers, tissues, wet wipes and a flashlight.
“People are really worried right now,” she said. Her husband, Volodymyr Stelmakh, who has another stand nearby, agreed.
“I’ve prepared an emergency bag,” he said, “but I think if the nuclear threat is imminent, you won’t have time to run away.
After concerns over the safety of the Zaporizhzhia nuclear power plant in the southeast of the country grew in recent weeks, Ukraine’s Health Ministry issued guidelines on how to respond to a nuclear incident.
The risk of nuclear fallout may seem very real in Ukraine, a country that still bears the scars of the Chernobyl accident in 1986, one of the worst nuclear disasters in history. Chernobyl is only about 60 miles north of Kyiv.
And some who have experienced the life-threatening fallout firsthand say they understand, perhaps more than anyone, the total risk of nuclear exposure. Oleksandr, 55, who asked that his surname not be used, said he and his family fled Chernobyl to Kyiv immediately after the collapse when he was just 18.
His family closely followed the advice to move south, as the winds were pushing the radioactive material north, and he said that was the only reason they got away unscathed.
“Now people here are really not ready. People don’t know what to do,” he said. “There is not enough information.”
He owns a market stall which sells necessities and said more people had come in the past two weeks to prepare for a nuclear disaster, buying flashlights, batteries, knives, radios and small camping stoves.
While some braced for the worst, others remained optimistic that Russia would never carry out such an extreme attack, which would spark international outrage.
Dmytro Yastrub, 31, said he felt more concerned about Mr Putin using conventional weapons to target Kyiv.
“I guess something will happen” after the bridge attack, he said, standing outside a bar in downtown Kyiv on Sunday evening with a group of friends. But, he added, the risk of a nuclear attack did not weigh heavily on his mind.
Svetlana Zozulia, 47, and her husband, Vladyslav Zozulia, 37, were strolling through central Kyiv with their daughter, Anastasiia, 11, on Sunday evening. Ms Zozulia said she was trying to remain optimistic and did not believe Mr Putin would launch a nuclear attack on Ukraine.
But she bought potassium iodide tablets just in case, she says.
“I think our success bothers him,” Ms. Zozulia said. “But there is also a threat to him if he chooses a nuclear attack.”
Oleksandra Mykolyshyn contributed reports