Air alert applications in both Ukraine and Russia were compromised by cyberattacks on Sunday night, dispatching false emergency warnings that included fabricated threats of nuclear attacks, radiation leaks, chemical hazards and street fighting.

The security breaches coincided with the end of the war’s longest localised ceasefire, implemented in Ukraine’s eastern Kherson region and brokered, in par, by US First Lady Melania Trump. The truce officially expired on Sunday after Russia declined to extend it.

For years, residents on both sides have come to depend heavily on these mobile applications for safety information as a vital lifeline against daily aerial bombardments. In Ukraine, where citizens have endured nearly five years of conflict, the compromised app abruptly pushed red-level air raid notices.

A Kyiv resident named Olena described the immediate panic to the BBC, stating: “The first thought was ‘oh my god, I’m not prepared for this’. I’m prepared for blackouts, for a cut in central heating and water supply, but not for nuclear attack.”

Olena noted that her husband subsequently received alerts for and messages written in Russian. She added: “After that I understood that somebody had attacked the app, because all notifications we get [are] in Ukrainian.”

In an official Telegram post, the Ukrainian air force urged calm, stating: “The Air Alarm application has probably been subjected to hostile interference. There is no radiation threat! Stay calm and follow our updates on our channel.”

Hours after the Ukrainian breach, Russian authorities confirmed that one of their air raid alert applications had also been targeted by a “massive cyberattack” that distributed false information to the public.

A purported screenshot shared by a partisan group operating in Russian-held territory warned users that “nuclear warheads mounted on P1-Suns [a Ukrainian attack drone] had been launched at all regions of Russia.”

The crude alert included profanities and told residents there was a “risk of [things] getting lively” before instructing them to “stock up urgently on food for three weeks and hide.”

While it remains unclear if the simultaneous cross-border hacks were directly connected or part of a retaliatory tit-for-tat exchange, cyber experts note that the informal language used in the hoax alerts pointed toward hacktivist networks rather than formal state directives.

Ukraine’s Centre for Strategic Communications placed blame directly on Russia, while Kremlin spokesman did not address the specific breach, noting instead that Russian government internet resources are under “constant cyberattacks” round the clock.

Both governments moved quickly to reassure the public and restore full functionality to their respective citizen safety platforms.

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