Japanese police have arrested four men, two of them from the Philippines, on suspicion of smuggling explosives and guns that could be used in a terrorist attack, domestic media said on Friday.
Police suspect the four shipped an unspecified quantity of explosives, along with revolvers and ammunition, to the port city of Yokohama on a Philippines-registered ship, Kyodo news agency said.
Investigators also searched premises belonging to a crime syndicate known as the Inagawa-kai in Yokohama in connection with the incident, Kyodo said.
Public broadcaster NHK said the weapons could be used in a terrorist attack.
Tokyo and Yokohama police declined to comment on the reports.
Japanese police said in a report last year that the country was at risk of attack because of its close links with the United States.
