The Chinese government warned that moves to prosecute the captain could damage bilateral relations, and said it was sending its own law enforcement ship to the islands in the East China Sea — though it was unclear if the vessel would simply collect stranded fishermen or patrol those waters.

The likelihood of a trial increased as the Japanese coast guard handed over 41-year-old captain Zhan Qixiong to prosecutors for further investigation to decide whether to officially charge him in the case, Japan Coast Guard spokesman Masahiro Ichijo said.

The captain has been in custody since his arrest Wednesday, after his ship collided with two Japanese patrol boats near the disputed chain of uninhabited islands. No one was injured, and the two Japanese vessels sustained minor damage.

Beijing reacted with swift criticism. Japanese Ambassador Uichiro Niwa has been summoned twice to see Assistant Foreign Minister Hu Zhengyue, who demanded that the Chinese vessel be released immediately. The crew, who do not have passports, are waiting on the boat.

The collisions happened in Japanese territorial waters off the northwestern coast of Japan’s Kuba island, just north of disputed islands known as Senkaku in Japanese and Diaoyu in Chinese. The islands, about 120 miles (190 kilometers) east of Taiwan, are controlled by Japan but are also claimed by China and Taiwan.

The captain could be released in a couple of days if he acknowledges the allegation of obstructing public duties resulting in the collision and pays a fine, Ichijo said. If not, he would likely have to stand trial.

Officials also were questioning the ship’s remaining 14 crew members, who are free to return to China, if the Chinese send a vessel to pick them up, the coast guard said.

The Chinese government has reiterated its claim to the Diaoyu, as well as its adjacent islets and their waters, urging Japan not to patrol there.

“The Japanese side applying domestic law to the Chinese fishing boat operating in this area is absurd, illegal and invalid,” Chinese Foreign Ministry spokeswoman Jiang Yu said at a regular news conference Thursday. China will not accept that, she added.

She said the territorial disputes are highly sensitive and improper handling would seriously affect “larger interests of China-Japan relations.”

Beijing has also sent “a fishery law enforcement ship” to the disputed area “to safeguard order in the relevant fishing area and protect the safety of fishermen and their assets,” Jiang said. She declined to say whether the ship would collect the remaining fishermen, or what it would do there.

Japanese Foreign Press Secretary Satoru Sato said Wednesday that Japan’s territorial ownership of the Senkaku is “the undeniable fact” and that the collision case should be investigated properly under Japan’s criminal law.

In Beijing, there was a small, organized protest Wednesday in front of the Japanese Embassy. About 30 people gathered to shout slogans and wave flags. Such events usually happen only with the approval of local police or officials.

China’s official media warned Thursday of setbacks to relations if Japan does not release Zhan.

“A wave of indignation is also brewing in Chinese society, which might snowball in a major public outcry if the Japanese authorities continue to take a hardline stance on the incident,” the English-language China Daily said in an editorial. “Each time it chooses to provoke China over the Diaoyu Islands issue, it puts bilateral relations at risk.”

But Japan’s largest newspaper Yomiuri defended the captain’s arrest as “legitimate,” adding that “China’s territorial claim is clearly unreasonable.” It said Beijing started its territorial claims over the islands only after the area became known as rich ground for undersea resources in the 1970s.

Territorial disputes have been a disruptive undercurrent in Japan-China relations. As the robust Chinese economy’s demand for resources grows, China’s commercial ships are venturing farther from shore and its more powerful navy is enforcing claims in disputed waters.

Last month, a Chinese survey ship allegedly entered Japan’s disputed exclusive economic zone without prior notification, breaking a previous agreement between the two countries. In April, a Chinese helicopter came within 300 feet (90 meters) of a Japanese military monitoring vessel in the vicinity of a Chinese naval exercise.

The latest incident occurred during a seasonal surge of Chinese fishing boats in the disputed area in recent weeks.

Since mid-August, the coast guard spotted as many as 270 Chinese fishing boats near the disputed islands per day, with 70 of them entering Japanese waters, Ichijo said, adding that it’s generally a seasonal trend due to increase of fish in the area.

The collisions occurred after the Chinese ship refused to stop for an inspection by the patrol vessels after repeatedly ignoring their earlier warnings to leave the area, the coast guard said.

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Associated Press Writer Alexa Olesen contributed to this report from Beijing.

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