An unnamed "state actor" was most likely behind the hacking of thousands of Dutch police contact details last week, the country's justice minister said on Wednesday.
David van Weel revealed the data leak Friday, which Dutch media reports said contained details of almost all 65,000 police officers in the Netherlands.
"The intelligence and security services consider it highly likely that a state actor is responsible" for the hack, Van Weel said in a letter to parliament.
He did not name a specific country.
News about the stolen details -- which Van Weel said contained "names, email addresses, telephone numbers and in a few cases, personal data" -- caused a major uproar among police personnel.
"I can imagine that police officers are concerned about the possible consequences of the hack," Van Weel said.
"The chief of police and I take this hacking incident very seriously," the minister added.
"The police, together with national security partners are doing everything they can to protect police officers and prevent further damage," he said.
Neither police, nor the country's security services gave further information, saying the investigation was ongoing.
The Dutch Military Intelligence and Security Service in February said it had discovered malware in a computer network being used by its military, blaming a Chinese state actor.
Beijing strenuously denied the "groundless accusations" saying it always opposed and cracked down on cyberattacks.
In April 2018 the Netherlands expelled four alleged agents from Russia's GRU military intelligence agency for trying to hack the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague.
The Dutch broke with their usual practice of keeping such operations secret and exceptionally revealed details of the plot in October, in coordination with US and British authorities.