A 50-year-old man was arrested Tuesday on initial suspicion of discarding the dismembered corpse of his 24-year-old ex-girlfriend, who vanished last month after telling police she was being stalked, the police said.

Keitaro Saga, unemployed and of no fixed address, is suspected of dumping the dismembered body of Shiori Nakamoto in rivers in Saitama Prefecture sometime between Sept. 17 and 20. Saga has confessed to killing Nakamoto, cutting her body up and throwing her remains into the Tone and Arakawa rivers, they said.

He also reportedly told investigators that he had dumped parts of her body down a drain at Nakamoto's house.

Police often arrest a murder suspect on an initial charge of dumping the victim's body in order to be able to detain the suspect while gathering further evidence to pursue homicide charges.

The company that Nakamoto worked for told the police in mid-September that she had failed to turn up for work.

Saga and Nakamoto, who apparently first met last November, had lived together in Tokyo until this spring.

After they broke up, the Saitama Prefectural Police arrested Saga on July 16 for allegedly assaulting Nakamoto.

He was released about 10 days later after submitting a letter to the police promising not to approach Nakamoto.

Afterward, Nakamoto filed a complaint with the police, claiming she was being stalked around her home in Tokyo. The police suggested she move and change jobs, advice that she rejected due to her financial situation.