STOCKHOLM, May 9, 2025 (BSS/AFP) - Sweden's new national security advisor has resigned just hours after being appointed after old photos of a "sensitive nature" from a dating app emerged, the government said Friday.

Prime Minister Ulf Kristersson acknowledged "a systemic failure" in government security clearance procedures.

Tobias Thyberg, a 49-year-old diplomat who has served as Sweden's ambassador to Ukraine and Afghanistan among other positions over a 24-year career, was appointed to the position on Thursday.

He quit the job less than 12 hours later after newspaper Dagens Nyheter (DN) confronted him with photos of a "sensitive nature" from his past.

"These are old photos from an account I used to have on (gay dating app) Grindr. I should have informed (the government) about this but I didn't," he told DN.

"I have therefore said that I do not plan to take up the position as national security advisor."

DN did not provide any details about the photos' content, but tabloid Expressen reported they were of a "sexual nature".

Prime Minister Kristersson, speaking to reporters in Oslo on Friday, called the matter "serious".

He acknowledged failures in security clearance procedures, as Thyberg has held numerous positions involving classified information for many years.

"It is a systemic failure that this (information) has not emerged," Kristersson said.

An intelligence expert at the Swedish Defence University told DN the photos were likely already in the hands of foreign powers, which could potentially use them as blackmail.

"I wouldn't be surprised if other countries' intelligence agencies already had this information," Johan Holmlund said, citing the United States, Russia and China.

The affair is particularly embarrassing for Kristersson because of a scandal surrounding Thyberg's predecessor.

Henrik Landerholm resigned in January after it emerged that he had forgotten classified documents at a hotel conference centre in March 2023.

He has been charged with "carelessness with secret information".

Landerholm's appointment two years ago sparked debate due to his longstanding friendship with Kristersson.

He left the documents in an unlocked locker and the woman who found them, originally from Georgia, "can be linked to violent extremism circles", according to the charge sheet and police investigation.