Ukraine’s air raid alert app was apparently hacked on Sunday and for a short time said the capital Kyiv was subject to a radiation threat, the Ukrainian Air Force has said.

The Air Force message on Telegram read: “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.”

The Ukrainian Central Intelligence Agency said on Telegram that there had been a failure in the app, and urged people to use other sources of information to clarify the situation regarding the threat of air strikes.

The messages, in Ukrainian, started at approximately 22:47 (20:47 GMT), with the first reading: “Radiation threat. Radiation threat declared in Kyiv.”

The next alert, written in Russian, came at 22:48, which read: “Hi! There will be a nuclear alert across Ukraine. Don’t worry, it’s Oreshnik flying”.

A third alert, at 22:49, again in Ukrainian, said “Chemical threat. There is a threat of a chemical attack on Kyiv. Don’t go outside.”

At 22:49, a fourth alert stated there was a “Street fighting threat. Street fighting is taking place in Kyiv. Don’t go outside.”

A series of all clear messages were then delivered to users’ phones, which were connected to each of the previous alerts, individually declaring each threat clear.

In a separate post, the Ukrainian Central Intelligence Agency said that due to the Air Alert application, the Radiation Hazard signal was played on loudspeaker devices in the Lviv region, and added there was no threat of radiation hazard.

It advised the public to turn on notifications on your smartphone, pay attention to sirens, and to only read official sources.

The governor of Vinnytsia oblast, Natalya Zabolotna said there had been a cyberattack on the Air Alert app and posted a warning on Telegram not click on the link in the message.

The Air Alert app is supported by the Ministry of Digital Transformation of Ukraine, and informs users instantly about the beginning and end of defence alerts.