Japanese investigative sources say as many as five Japanese nationals being held at a Philippine immigration facility may have used a third-party social media account to communicate with a group that has carried out a series of robberies in Japan.

Japanese police believe the suspect or suspects, who went by the alias "Luffy," used the third-party account to avoid being identified.

They say the suspects in Manila may have used the alias in order to give instructions to their accomplices in Japan.

The police believe the group oversaw robberies carried out in Japan while using social media to recruit new perpetrators.

They have requested that Philippine authorities hand over the Japanese detainees in question, including Watanabe Yuki, who is believed to be a key member of a fraud group based in the Philippines.