Chief Cabinet Secretary Yoshito Sengoku said Friday that China and Japan, the two major economic powers in Asia, need to work toward improving bilateral relations.

"It is true that Japan-China relations have shown signs of deterioration," Sengoku, Japan's top government spokesman, said at a press conference, adding that efforts were needed to deepen bilateral relations between the two countries.

The comments came as the Naha, Okinawa, prosecutor's office said Friday it will release Zhan Qixiong, the 41-year-old Chinese fishing boat captain who has been held for more than two weeks.

Two Japan Coast Guard patrol ships and a Chinese trawler collided in waters off China's Diaoyu Islands on Spet. 7.

The next day, the Japan Coast Guard illegally seized the Chinese trawler and detained its captain and 14 fishermen on board, drawing strong protests from the Chinese government and its people.

The Japanese released the fishermen and boat last week but held the captain. China has repeatedly urged Japan to unconditionally send back the captain to avoid additional damage to their bilateral ties.

According to local media, Zhan was to leave Japan on Friday. Chinese Foreign Ministry spokeswoman Jiang Yu said the same day the Chinese government would send a chartered plane to bring back the captain.