(File photo: AFP)

A Japanese tourist detained in North Korea will be released "on the principle of humanitarianism", Pyongyang's state media reported as Tokyo seeks a summit with the North amid a diplomatic thaw on the peninsula.

"Tomoyuki Sugimoto, who visited the DPRK as a Japanese tourist recently, was kept under control by a relevant institution to be inquired into his crime against the law of the DPRK," the KCNA news agency said.

Little is known about Sugimoto but Japanese media reports have said he was a videographer visiting the North on a tour arranged by a foreign travel agency.

He may have been suspected of shooting video of a military facility in the western port city of Nampo, reports cited Japanese government sources as saying.

It was not clear if Sugimoto had been charged with any crime and the KCNA report late Sunday did not provide details on when he would be released.

"The relevant institution of the DPRK decided to leniently condone him and expel him from the DPRK on the principle of humanitarianism," it said.

The Japanese foreign ministry declined to comment to AFP.