Prosecutors on Thursday demanded the death penalty for the man indicted over the 2017 serial murder of nine people who had expressed suicidal thoughts on social media, in a high-profile case that shocked the nation.

At a lay judge trial at the Tachikawa branch of the Tokyo District Court, prosecutors sought the death penalty for Takahiro Shiraishi, 30, who pleaded guilty to murdering, dismembering and storing the bodies of the nine in his apartment in Zama, Kanagawa Prefecture.

"Nine young lives were taken in such a short period of two months," a prosecutor said, adding that his crimes "deserve death."