A man in his 20s will stand trial for threatening to kill 20 women in Seoul's Sillim area following last month's deadly stabbing spree.

The Seoul Central District Prosecutors' Office on Friday indicted the 26-year-old, identified by his surname Lee, on charges of preparation for murder, intimidation and violation of the information communications network law for his online threat.

This is the first time that prosecutors applied the preparation for murder charge in an indictment against a suspect who has threatened to commit a copycat crime following the Sillim rampage.

The state agency believes that Lee planned to actually carry out the killings after they discovered that he had purchased a 32-point-five-centimeter-long knife three days after the Sillim incident as well as online photo searches of serial killers Yoo Young-chul and Lee Chun-jae.

Lee had also posted over one-thousand-700 hateful messages against women since March of this year.

Amid a recent uptick in the number of similar online threats, the National Office of Investigation(NOI) announced that as of 9 a.m. Friday, it has apprehended 119 people, 12 of whom have been arrested.