Police in Tokyo have arrested seven people in connection with the robbery last year of cash worth over 270,000 dollars from a home in a Tokyo suburb. The arrests are part of a widening police investigation into a recent string of robberies around Japan.

The police suspect that the seven may have been recruited and instructed through social media by a person called Luffy, believed to be in the Philippines.

Last October, the seven allegedly broke into the home in Inagi City after pretending to be from a parcel delivery firm, assaulted a female resident and bound her and members of her family with adhesive tape. They then allegedly made off with a safe containing about 35 million yen in cash and gold bars worth around 8.6 million yen.

A police analysis of mobile phones confiscated from some of the arrested shows that Luffy may not have been the only one giving instructions. Two more names, Kim and Mitsuhashi, have also emerged as those of possible ringleaders.

Three of the seven had already been arrested and indicted in an attempted robbery case in Iwakuni City, in the western prefecture of Yamaguchi, last November.

The police are investigating suspected links between some of the seven and similar cases. They include the robbery-murder of a 90-year-old woman this month in Tokyo's Komae City, a robbery-assault case in Tokyo's Nakano Ward last month, and an attempted robbery-murder last month in Hiroshima City, western Japan.