Fake nuclear warnings in Ukraine as Moscow, Kyiv report separate cyberattacks on emergency apps

Ukraine's Air Force said Sunday its Air Alert app had been compromised after it reportedly sent false warnings of nuclear and chemical threats in Kyiv and other areas.

The app briefly displayed alerts for nuclear and chemical incidents, as well as warnings of street fighting, according to Reuters. The Air Force said unauthorized persons had interfered with the app's operation and that it had temporarily disabled push notifications.

"There is no radiation threat! Stay calm, follow our messages on our channel," the Air Force said on Telegram, according to a translation.

Two hours later, Russia's Ministry for Emergency Situations said its mobile app had been subject to "a massive cyberattack, allowing attackers to send fake information to the public."

It was not immediately clear if the incidents were linked. CNBC has reached out to Russian and Ukrainian authorities for comment.

The alleged cyberattacks come as Russia and Ukraine continue to trade strikes on each other's territories and infrastructure.

Overnight, a local ceasefire in the devastated Russian-occupied city of Oleshky and surrounding areas in the Kherson region, near the Crimean Peninsula, expired. The temporary pause in fighting allowed humanitarian aid to enter the city and the evacuation of hundreds of people who had been trapped largely without access to food, water, electricity, and medicine.

It was the longest local ceasefire since the full-scale invasion began in early 2022, and both parties appeared to have honored the pause until it ended at midnight Moscow time.

On Monday morning, local media reported that Russian forces had struck a hospital in central Kherson, while Ukraine's General Staff of Armed Forces said Moscow had used the ceasefire to reinforce its military positions in the city.

"During the ceasefire, the rotation of Russian units, the fortification of positions, the expansion of anti-drone measures along roads and increased logistics activity, including the delivery of ammunition, were recorded," the military body said early Monday.

On Sunday, President Volodymyr Zelenskyy said October had been the deadliest month for Russia since the invasion began in 2022.

Over the past month, Russia lost 54,400 troops killed or badly wounded, "a record for any month of the full-scale war," Zelenskyy said, adding that Ukraine's Defense Forces liberated 96.2 square kilometers of Ukrainian land in October – 10.4 square kilometers more than Russia captured during that time.