The Polish government said Friday that a false story stating that Poles would be mobilised to fight in Ukraine that appeared on the state news agency was likely a Russian cyberattack.
The Polish Press Agency (PAP) deleted the article a few minutes after it was published on Friday, and said it did not originate with them.
The article then appeared a second time and was deleted again.
"Given the probable Russian cyberattack on the Polish Press Agency and the release of disinformation on alleged mobilisation in Poland, the ABW (internal security agency) and the digital ministry have taken swift action," security services spokesman Jacek Dobrzynski said on X.
The PAP said it was "investigating the circumstances around the appearance of the false story".
"The source of the text is not the Polish Press Agency," it added.
The false article claimed that Prime Minister Donald Tusk had said Poland would announce a partial mobilisation on July 1.
"Two hundred thousand Polish citizens, both ex-military and regular civilians, will be called up for mandatory military service," the article claimed.
"Everyone called up will be sent to Ukraine," it added.
The text featured several red flags including a lack of quotes, no precise source, a verbose writing style and no initials at the end.
Poland is not the first country to see its news agency hacked in recent months.
In April, hackers attacked the website of the public Czech news agency CTK, posting two fake texts saying the Czech intelligence service had prevented an attack on Slovak president-elect Peter Pellegrini.
Czech police and the Security Information Service are investigating the case.