An unemployed South Korean man has been booked for investigation after he cut off part of his left pinky and sent it to the Japanese embassy in protest of Tokyo's territorial claim to South Korea's easternmost islets of Dokdo, police said Wednesday.

The 47-year-old, identified by his family name Choi, cut his finger in front of the embassy in April before having surgery to stitch it back on, said Lee Jong-wook, a police detective, who handled the case.

Choi took the extreme action a month after Tokyo approved a set of new middle school textbooks that describe Dokdo as Japanese territory. The claims, though not new, have sparked public resentment against the former colonial ruler.

Choi also traveled to Seoul in May to protest against Japan's territorial claims. During the protest, he cut off the same portion of his pinky again. After doctors told him that the finger cannot be stitched on again, he sent it to the embassy by delivery service, the detective said.

Choi told police investigators that he sent his cut-off pinky because he was upset by the Japanese territorial claims to the islets despite Seoul's humanitarian aid to Japan.

South Korea offered donations to Japan over the devastating earthquake and tsunami early this year, though many South Koreans later resented against Tokyo's sovereignty claim to the rocky islets.

The Japanese territorial claim has been at the center of long-running diplomatic friction between the two neighbors. Japan ruled the Korean Peninsula between 1910 and 1945 as a colony.

Choi was not in police custody, and police referred the case to the prosecution in September, said Lee.

Prosecutors and Choi were not immediately available for comment. (Yonhap News)