A Japanese man who is suspected to have instructed a recent series of robberies across Japan had his girlfriend repeatedly bring defrauded money four years ago from Japan to the Philippines, where he is based.

Japanese police believe that Watanabe Yuki is a member of a group linked to phone scams in Japan and had given instructions from the Philippines in the series of violent robbery cases in Japan.

Tokyo police have already obtained an arrest warrant for Watanabe, who is now being held at an immigration facility in greater Manila, for fraud cases in Japan.

His girlfriend, aged 32, was found to have repeatedly traveled to Manila in 2019 to deliver what are believed to be bundles of cash swindled from victims in Japan to Watanabe.

Police and other sources say the woman was arrested in November 2019 for stealing cash cards from an elderly victim by making phone calls pretending to be a police officer.

She was handed a prison sentence of four years and six months by the Osaka District Court for her involvement in several phone scams in October 2020.

The court ruling said that the woman began associating with Watanabe, who claimed to be a businessman, after first meeting him in Manila in March 2019.

The court said she visited Manila again in the following month at Watanabe's invitation and handed him 20 million yen, or about 155,000 dollars, in cash she took out from Japan.

Police investigations confirmed that the woman traveled from Japan to the Philippines seven times in 2019. She is believed to have carried tens of millions of yen with her each time.

The court found her guilty, saying the fraud group also had a base in the Philippines, and the woman played an important role in securing the money the group gained from its crimes.

Investigative sources say a spate of phone scams took place around four years ago across the country that were believed to have been carried out by the group. They say the name Watanabe, who was in Manila at that time, had surfaced in the course of the investigation into his girlfriend.

Japanese police have requested the Philippine authorities to hand over Watanabe and three other Japanese nationals also under detention in Manila in connection with the fraud cases. These men are also suspected to be linked to the robberies in Japan.