A South Korean history institute has filed a defamation suit against three Japanese accused of setting up provocative wooden stakes in downtown Seoul last month to lay claim to Dokdo, police said Tuesday.

Two Japanese suspects in their 30s and 60s allegedly put three wooden posts with the phrase, "Takeshima (referring to Dokdo in Japanese) is Japanese territory," at the entrance to the Dokdo Research Institute under the state-run North Asian History Foundation in Seoul last month.

The two men also put stakes at the Korean Council for Women Drafted for Military Sexual Slavery by Japan on the same day.

Seoul's Seodaemun Police Station said the complaints against the two men and Nobuyuki Suzuki, a member of an ultra-right Japanese party who reportedly ordered the vandalism, were filed on Monday.

"We plan to locate the whereabouts of the suspects and notify them to come to Seoul for questioning," an official in charge of the investigation said. "However, it is unclear whether they would honor summonses."

Meanwhile, the council, which represents voices of a group of Korean women who were coerced into sexual servitude for Japanese troops during World War II, has reportedly decided not to take any legal action against the suspects.

Wrapping up an internal investigation into the vandalism, police authorities last month said the two are also suspected of attaching leaflets to a wall that said in English, "Comfort Women = Sex Slave is Lie." The victims are euphemistically called "comfort women."

The Justice Ministry has banned the entry of the two suspects as well.

It was later revealed that Suzuki, who is currently snubbing prosecutors' summoning for questioning in connection with a separate defamation suit, had masterminded the attacks.

Suzuki was earlier sued by a group of comfort women in connection with a controversial wooden post he tied to a symbolic statue of a sex slave in front of the Japanese Embassy in downtown Seoul in June.

Japan, which ruled the Korean Peninsula between 1910 and 1945 as a colony, has repeatedly renewed its claim to Dokdo in the East Sea while rejecting Seoul's demand for an apology and talks on compensating the sexual slavery victims. (Yonhap News)