False nuclear alerts hit Ukrainian and Russian warning apps

False warnings of radiation, nuclear weapons and other threats reached people in Ukraine and Russia after emergency alert apps in both countries were hit by cyberattacks, authorities said. The messages began Sunday night, as a six-day humanitarian ceasefire in Russian-occupied southern Ukraine came to an end.

In Ukraine, users of the Air Alert app received warnings of radiation and chemical hazards, street fighting and a nationwide nuclear alert. One message, written in Russian, told recipients not to worry because “Oreshnik is in action,” referring to Russia’s nuclear-capable hypersonic missile.

Ukraine’s Air Force said the app appeared to have been compromised and urged people to stay calm. “There is no radiation threat!” it said. The app’s creators said unauthorized third parties had interfered with the service. They temporarily suspended it before beginning to restore it and said they were taking additional steps to prevent a repeat.

Ukrainian media reported that users across the country received the messages. Authorities in the western Lviv region said some public sirens and loudspeakers also broadcast a radiation warning, according to NBC News. Al Jazeera reported that speakers in central Kyiv sounded warnings, but that most people there understood within about half an hour that the alerts were false. Some Ukrainians mocked the messages online, including their use of Russian.

Ukraine’s Center for Strategic Communications blamed Russia, pointing to the Russian-language message, Al Jazeera reported. Ukrainian authorities said a separate alert app for Kyiv was working normally. By Monday, Ukraine’s State Emergency Service said the national alert system was operating normally.

Hours after the Ukrainian alerts, Russia’s emergencies ministry said its own mobile warning app had suffered a “massive cyberattack” that spread false information. Russian media and regional authorities shared screenshots of messages warning that nuclear warheads had been launched toward Russia, NBC News reported. Al Jazeera said the Russian alerts also warned of imminent drone attacks and instructed people to stock up on food and hide.

The Russian ministry said its app had been restored. It did not identify the attackers, and it was not clear whether the incidents in the two countries were connected.

The alerts followed the end of a localized ceasefire in the occupied Kherson region. The six-day truce allowed humanitarian aid and the evacuation of hundreds of residents from the town of Oleshky, according to NBC News. The United States said first lady Melania Trump helped broker the agreement; NBC News also reported involvement by Pope Leo XIV.

“I hope Oleshky serves as a foundation for lasting peace between both nations,” Trump wrote Sunday. Ukrainian human rights ombudsman Dmytro Lubinets said he was exploring further humanitarian initiatives with his Russian counterpart, Yana Lantratova.

The ceasefire ended amid disagreement over how the sides had used the pause. Ukraine’s armed forces accused Russia of rotating troops and strengthening positions. Kremlin spokesman Dmitry Peskov said Ukraine could also have used the truce to regroup, calling that a “completely common practice in such situations.”