False alerts warning of an imminent nuclear strike and chemical attack spread rapidly through Ukraine's official Air Alert app late Sunday night, causing panic in multiple cities as sirens sounded nationwide.

The messages began appearing around 10:47 p.m. local time on November 1. One notification in Russian stated, "Hi! A nuclear alert is about to go off all across Ukraine! Don't worry, the Oreshnik is on its way." Other alerts warned of radiation threats in Kyiv and chemical dangers, prompting residents to receive notifications on their phones via the app developed with the Digital Transformation Ministry.

Air raid sirens activated in regions including Zakarpattia Oblast in western Ukraine. Loudspeaker hazard signals also sounded in the Lviv region due to the app's false radiation warning.

Ukraine's Air Force quickly responded on its Telegram channel, stating that the app had likely been compromised by the enemy and confirming there was no radiation threat. Officials urged the public to stay calm and monitor official updates. The Ukrainian Central Intelligence Agency and regional governors, including those in Vinnytsia and Ivano-Frankivsk, echoed the message and advised against clicking unknown links or sharing unverified information.

The false alerts were cleared within about an hour. By midnight, the State Emergency Service reported that the nationwide system had returned to normal operation, though citizens were told to continue verifying information through local authorities.

This incident occurred amid ongoing Russian strikes on Ukraine's energy infrastructure, including substations that connect nuclear power plants to the grid, which have caused rolling blackouts in cities like Kyiv and Dnipro. The cyberattack on the alert system added to civilian disruption during the prolonged conflict.

Ukrainian officials described the event as a hostile interference with the notification app and confirmed investigations into the breach. The episode highlighted vulnerabilities in digital warning systems relied upon by millions during air raids.