Police in Tokyo have arrested four officials at a staffing agency on suspicion of having a Vietnamese work illegally.

Those arrested are managing director Yamakawa Tomokazu and three others of Motoki Shoji, based in the city's Toshima Ward.

Japan is clamping down on exports of seeds and saplings as it looks to protect its food industry.

A revision to Japan's Plant Variety Protection and Seed Act on Wednesday allows developers to limit export destinations, as well as production areas in Japan, for registered new varieties of crops.