According to BBC News, "Around 40 Delhaize supermarkets in Belgium and Luxembourg were affected, while several ICA and Coop shops in Sweden were hit. Thirteen SuperValu shops have also been impacted in Ireland."

One store in Sweden said the attack caused its refrigerators to reach a temperature of 122F.

Millions of euros worth of food has had to be thrown away.

A similar attack on French supermarkets took place last month. Hundreds of stores were affected.

It's unclear if the attacks are linked.

Cyber-security agencies in Belgium and Sweden say they are monitoring the situation.

On Sunday, Russia and Ukraine had their emergency-alert systems hacked within hours of each other, causing a series of fake warnings to be issued.

NBC News reports, "The messages, which began around 10:45 p.m. Kyiv time (3:45 pm ET), warned residents not to go outside because of radiation hazard, chemical threat and street fights.

"Another message professed, in Russian, that all of Ukraine was under nuclear alert. 'Don't worry,' it added. 'Oreshnik is in action,' referring to Russia's nuclear-capable hypersonic missile.

"Shortly after the alerts went out late Sunday, Ukraine's Air Force said the country's 'Air Alert' app had likely been 'compromised by the enemy,' confirming there was no 'radiation threat' and urging calm."

Ukrainian media reported that users across the country received the fake alerts.

It's also reported that in some places warning sirens and loudspeaker systems broadcast a "radiation hazard" signal.

Russia also confirmed it had suffered a "massive cyberattack" leading to "dissemination of fake information to the public."

At least one of the fake alerts warned of "nuclear warheads" being launched at Russia.

The hacks came not long after a temporary ceasefire ended between the two countries in the occupied region of Kherson.