The suspects are all current or former employees at Denmark's two intelligence services.
Four people have been arrested in Denmark on suspicion of leaking confidential information from the country's security services.
The suspects are all current or former employees at Denmark's two intelligence agencies, the domestic Danish Security and Intelligence Service (PET) said on Thursday.
"PET, in cooperation with the police, yesterday arrested four people and conducted searches at a number of different addresses," a brief statement read.
The four people are alleged to have disclosed "highly classified information from the intelligence services". They reportedly face up to 12 years in prison if found guilty.
Denmark's other intelligence agency is the Danish Defense Intelligence Service, known by the acronym FE.
The authority said the four arrests came after a lengthy, ongoing investigation. The identities of the suspects were not revealed.
"The cases have now been transferred to the public prosecutor," the PET said, without commenting further.