People gathered at dusk Sunday at a number of locations nationwide to mourn the deaths of Kenji Goto and Haruna Yukawa, two hostages of the Islamic State group whom the militants apparently murdered last month.

Near the statue of Hachiko outside Shibuya Station in Tokyo, a popular landmark where crowds mill about on usual weekends, was enveloped in an unusually somber mood after people bearing candles and placards started to gather. The quietly standing people eventually filled the entire area.

Participants had responded to messages on Twitter, Facebook and other social networks, saying the spontaneous calls to gather had grown naturally as they were relayed.

"I had hoped he'd come back, so it's sad," said Julia Maeda, who came with her husband and children, holding a candle in her hand. "I think the onus is on us all to keep his wishes for peace alive," added Maeda, who was a friend of freelance journalist Goto.

Shiori and Nanami Katori, who came to the site together, stood holding placards saying: "May rest in peace. In memory of Kenji Goto (and) Haruna Yukawa."

"I kept wishing Goto-san would come back alive," said Shiori Katori, who then choked and fell silent.

Nanami Katori said: "We're their compatriots, but couldn't do anything for them. I felt useless."

Similar gatherings reportedly took place at locations in Tokyo, Osaka, Nagoya, Kyoto, Sapporo, Sendai, Chiba and Fukuoka.