NHK has learned that Japan has stationed a narcotics control agent in Hong Kong to strengthen information-gathering on drug smuggling attempts.
The health ministry last year assigned an official from the narcotics control department as a consul at a consulate-general there.
Chief Cabinet Secretary Suga Yoshihide says the Japanese government continues to watch the situation in Hong Kong with grave concern.
Suga spoke to reporters on Tuesday after Hong Kong police arrested pro-democracy activists and a media tycoon under the territory's new national security law.
The foreign chiefs of Japan and Britain have agreed to work together to respond to the coronavirus and the situation in Hong Kong.
Japanese Foreign Minister Motegi Toshimitsu met his British counterpart Dominic Raab in London on Wednesday. They talked for about two hours.
Japan is keeping an eye on Hong Kong to see how the implementation of China's national security law for the territory will affect its democracy and Japanese business activity there.
China's top legislative body enacted the national security law on Tuesday to crack down on anti-government protests.
Japanese Prime Minister Abe Shinzo says Japan will play a leading role in the Group of Seven economic powers issuing a statement on Hong Kong affairs.
Abe said in the Diet on Wednesday that Japan has expressed concern over developments in Hong Kong, following China's decision to introduce national security legislation aimed at cracking down on anti-government protesters in the territory.