Japan is weighing what to do with 14 people it arrested after pro-China activists landed on a disputed island, with China angrily demanding their immediate release.
Five of the activists, who were arrested on the island on Wednesday, were in the Okinawan capital Naha where they would face questioning, police said on Thursday.
The other nine detained at sea were set to arrive later in the day.
"They were already taken to Naha city [in Okinawa], and questioning will start today at separate police stations," a local police officer told AFP news agency, referring to those arrested on land.
A spokesman at the local coast guard said: "The nine arrested yesterday are to arrive at the port of Naha in the evening."
Japan arrested the activists on Wednesday from the Action Committee for Defending the Diaoyu Islands group that sailed from Hong Kong, saying that they intended to plant a Chinese flag after landing on an archipelago they know as Diaoyu, but which Japan calls Senkaku.
The row over the islands in the East China Sea, which are near potentially vast maritime gas fields, has frayed relations between the two Asian neighbours.
The ties have long been plagued by the bitter legacy of Japan's wartime occupation of much of China and contemporary rivalry over resources and regional clout.
Japan and China traded protests over the incident, with Tokyo lodging a complaint with the Chinese ambassador and Beijing demanding their unconditional and immediate release.
The Chinese government allowed a rare and brief protest in front of the Japanese embassy in Beijing on Wednesday, where a small group of people shouted anti-Japanese slogans before peacefully dispersing.
Riot police and plain-clothed security guards surrounded the embassy again on Thursday, as more protests were expected.
Against this backdrop, about 30 people protested at the Japanese consulate in Hong Kong on Thursday, chanting slogans and demanding the activists' release.
Yoshihiko Noda, Japan's prime minister, on Wednesday said Japan would "deal with the incident strictly in line with the law".
Japan's foreign ministry said it had summoned the Chinese ambassador to Tokyo to register its displeasure at the landing.
Beijing countered by saying it would lodge a complaint over the arrests.
Leung Chun-ying, the Hong Kong chief executive, also said he will "closely" monitor the incident and that the city's immigration officials will be in Japan to provide assistance to the activists.
The Okinawan prefectural police are expected to either turn the detainees over to immigration authorities for deportation or send the case to prosecutors for further investigation.
The case is a delicate one for Japan, which has to balance popular annoyance at the landing with vehement demands from China for the immediate release of the group.
The activists had said the move was aimed at countering a plan by a group of Japanese lawmakers to visit the disputed islands this weekend.
"We're very happy, we have tried many times and we declare this trip a big success," Chan Yu-lam, spokesperson for the Action Committee for Defending the Diaoyu Islands, said in Hong Kong on Wednesday.
Local media on Thursday speculated that the authorities would deport the 14 within a few days.
Under Japanese law, a foreigner who does not have permission to be in Japan can be turned over to immigration authorities for immediate deportation when the individual is not facing other criminal charges.
In 2004, when a group of Chinese activists landed on a disputed island, the then prime minister Junichiro Koizumi ordered their deportation after two days.