Chinese Foreign Ministry Wednesday lodged strong protest against Japan over the detention of a Chinese fishing boat and its crew near the Diaoyu Islands in the East China Sea.

The ministry demanded the Japanese side to release the detained Chinese ship and crew members and guarantee their safety.

Chinese Assistant Foreign Minister Hu Zhengyue summoned Japanese ambassador to China Uichiro Niwa Wednesday to lodge the protest, which was the strongest wording so far after the incident.

Within 24 hours, the Chinese government summoned the ambassador on this issue for the second time.

Two Japanese patrol boats collided with a Chinese fishing boat in waters off the Diaoyu islands Tuesday. No injuries were reported from the collision, but then the fishing boat was intercepted by Japanese patrol boats.

On the same day after the incident, Chinese Vice Foreign Minister Song Tao summoned Uichiro Niwa and urged Japanese patrol boats to stop their illegal interception of Chinese fishing boats.

Wednesday morning, Japan's Coast Guard arrested the captain of the fishing trawler despite China's requests.

The captain was taken to Ishigaki Island in Okinawa Prefecture at around 7 a.m. and the 14 Chinese crew were also taken to Ishigaki in the afternoon but were barred from disembarking, according to media reports.

Immediately after the arrest, Chinese ambassador to Japan Cheng Yonghua lodged solemn representations to Japan. The Chinese embassy in Japan has sent personnel to visit the Chinese fishermen being held at Ishigaki Island.

The trawler captain, a 41-year-old Chinese national, will be taken to the prosecutors or police nearby and will be questioned under Japanese procedures, according to media reports.

On Tuesday, Foreign Ministry spokeswoman Jiang Yu said that China demanded Japanese patrol boats refrain from so-called law enforcement activities in waters off the Diaoyu islands and refrain from actions that would threaten the security of Chinese fishing boats and crew.

"The Diaoyu islands and its adjacent islets have been Chinese territory since ancient times," Jiang said at a regular press conference when asked to comment on the collision.

"We will closely follow the situation and reserve our right to take further actions," Jiang said.

Fishermen from China's Taiwan and Fujian and other provinces conducted activities such as fishing and collecting herbs in this area since ancient times.

"The Diaoyu islands have historically been a part of China's territory, and it is very normal for the Chinese fishermen to conduct fishing in our territorial waters," said Lu Yaodong, director of the Institute of Japanese Studies, Chinese Academy of Social Sciences.

Lu said Japan's law enforcement activities were groundless and illegal.

When it comes to the Democratic Party of Japan's (DPJ) Presidential election on Sept. 14, the ship collision incident might be used in the struggle between Japanese Prime Minister Naoto Kan and his rival Ichiro Ozawa, said Liu Jiangyong, professor with the Institute of International Studies, Tsinghua University.

Since the situation was "very complicated," Liu said the two countries should prevent the tension from escalating and make joint efforts to safeguard the stability of Sino-Japanese ties.