Russia has said its emergency warnings app came under a “massive cyberattack”, hours after Kyiv’s announcement that Ukraine’s air raid alert app was hacked.

Moscow’s Emergencies Ministry said on Telegram early on Monday morning that the cyberattack led to the spread of “false information” on the app, which warns users of incoming drone attacks.

The ministry did not say who was behind the cyberattack.

Earlier on Sunday evening local time, the Ukrainian Air Force said that users received fake alerts warning of nuclear and chemical threats to areas in and around Kyiv, along with warnings of potential street combat.

An erroneous message also said Russia’s hypersonic Oreshnik missile had been deployed.

“The air alert app appears to have been subjected to enemy influence,” the Ukrainian Air Force said on Telegram on Sunday. “There is no radiation threat! Stay calm and follow our updates on our channel.”

SPRAVDI, Ukraine’s Centre for Strategic Communications, blamed Russia for the hack in a post on X.

The air raid alert app is used across Ukraine to warn people in real time of incoming Russian air attacks. A separate app, specifically for the Ukrainian capital, was working normally, according to Kyiv authorities.

The announcements from Russia and Ukraine follow the end of a truce between the two countries in a part of the Russian-occupied Kherson region.

The localised ceasefire, which began on Tuesday and ended on Sunday, was the longest of the war so far.