The national security adviser to Slovakia's prime minister has resigned after documents released by the US showed he exchanged messages about girls and diplomacy with the late sex offender Jeffrey Epstein.

Robert Fico announced he had accepted Miroslav Lajčák's departure in a video message on Saturday, describing the adviser as "an incredible source of experience in diplomacy and foreign policy".

The resignation comes a day after three million files relating to the influential financier were released by the US Department of Justice.

While the files do not show any wrongdoing on the part of those featured, including Lajčák, they have raised renewed questions for those who associated with Epstein.

In a text exchange from October 2018 - when Lajčák was serving as Slovakia's foreign minister - Lajčák and Epstein could be seen lightheartedly discussing women and a forthcoming meeting with Russian Foreign Minister Sergei Lavrov.

After Epstein sent an image, which cannot be seen in the record, Lajčák replies: "Why don't you invite me for these games? I would take the 'MI' girl".

"Who wouldn't," Epstein texts back. "You can have them both, I am not possessive. And their sisters."

Later on in the conversation, Epstein can be seen imploring Lajčák to ask Lavrov to get him a t-shirt featuring Lavrov and Viltaly Churkin, a Russian ambassador to the UN who had died the previous year.

"You get the tee shirt. Then you get the girls," Epstein writes, to which Lajčák agrees.

Epstein then says: "No kidding their sisters are both swimming in the pool."

"That's not fair!" Lajčák responds.

"Though they're all under 30. So. Probably too young for you," Epstein adds. "Or should I say under 50."

"Don't be mean," Lajčák replies. "You don't know me in action."

In an email to Epstein in November 2017, Lajčák asks Epstein to help a female film producer get her movie on the shortlist for that year's Oscars.

Lajčák initially denied discussing women with Epstein when the files were released on Friday, according to Slovak media. He later reportedly said he had decided to resign to avoid damaging Fico politically.

Fico characterised the outrage in Slovakia over Lajčák's association with Epstein as "an attack against me".

"I have not seen so much hypocrisy in his criticism for a long time, and from all sides," he said.

Lajčák had served in four Slovak governments, three led by Fico, and as an international diplomat. The former foreign affairs minister had most recently been an EU special representative for the western Balkans.

The massive tranche of files released on Friday have revealed new details about the relationships Epstein - who died in custody in 2019 while awaiting trial on sex trafficking charges - had with high-profile figures, including Elon Musk, Lord Peter Mandelson, Bill Gates and Andrew Mountbatten-Windsor.

Among them are images of the former Duke of York, who was stripped of his titles over his association with the disgraced financier, that appear to show the former prince kneeling on all fours over a female lying on the ground.