Hackers send fake nuclear alerts in Ukraine and Russia

Emergency alert apps in Ukraine and Russia were hacked late Sunday and early Monday, sending millions of phones false warnings about nuclear, chemical and radiation threats.

In Ukraine, the widely used Air Alert app began sending messages around 10:45 p.m. local time telling people to stay indoors because of radiation, chemical danger and street fighting. One message, written in Russian, claimed all of Ukraine was under a nuclear alert. Ukraine's air force said the app had likely been compromised by the enemy and that there was no radiation threat. The app's developers suspended it temporarily and later restored the service.

Hours later, Russia's emergencies ministry said its own mobile app had suffered a massive cyberattack that spread fake information, including warnings of nuclear warheads launched at Russia. It said the system was quickly restored. Russia did not say who it blamed. It was not clear whether the two incidents were connected, and a pro-Russian hacking group claimed the attack on the Ukrainian app.

Officials in both countries said their main warning systems, such as sirens, kept working normally.

The hacks came as a six-day local ceasefire around the Russian-occupied town of Oleshky, in southern Ukraine, came to an end. The truce, brokered with the involvement of U.S. first lady Melania Trump, allowed hundreds of residents to be evacuated. Ukraine accused Russia of using the pause to strengthen its positions.