China’s foreign minister demanded on Friday that Japan immediately release the captain of a Chinese fishing boat that collided with two Japanese patrol vessels near disputed islands. But a Tokyo court ruled he can be held 10 more days, deepening the diplomatic spat.

Yang Jiechi made the demand to Ambassador Uichrio Niwa after the Japanese envoy was summoned for the third time over the crash.

Hours after Mr. Yang’s protest, a Japanese court allowed prosecutors to keep the captain in custody until September 19 before deciding whether to press charges against him, Naha District Court spokesman Yasuhide Yamashiro said.

China has said the confrontation could damage its relations with Japan, showing the sensitivity of the territorial dispute, one of several that trouble China’s ties with its Asian neighbours. As the robust Chinese economy’s demand for resources grows, Beijing’s commercial ships are venturing farther from shore and its more powerful navy is enforcing claims in disputed waters.

The collisions occurred Tuesday after the Chinese fishing boat ignored warnings from the patrol vessels to leave the area and then refused to stop for an inspection, Japan’s coast guard said.

The incident happened off 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.

Mr. Yang told Mr. Niwa that captain Zhan Qixiong, his crew and boat had to be freed immediately, a ministry statement said.

In Tokyo, Foreign Minister Katsuya Okada told a news conference on Friday that it was regrettable that Mr. Niwa had been summoned by Mr. Yang.

“We are only taking proper steps based on law because there was an alleged obstruction of public duties in our territorial waters,” Mr. Okada said.

On Thursday, Chinese Foreign Ministry spokeswoman Jiang Yu said it was “absurd, illegal and invalid” for Japan to be applying its domestic laws to the case.

The spat has stirred nationalistic passions in China, with newspapers and activists calling for a tough stand against any threats to China’s territorial claims.

“It is our territory and we’re entitled to exercise sovereignty,” said Sun Peng, a 32—year—old software developer in Shanghai who has campaigned against Japan.

Mr. Sun said diplomatic efforts with Japan were a waste of time.

Japan’s coast guard has said Capt. Zhan could be released in a few days if he accepts the allegation that he obstructed public duties, resulting in the collision, and pays a fine. If not, he would likely have to stand trial.

The other 14 crew members have remained on the fishing boat, the coast guard said. They cannot land in Japan because they do not have passports but are free to return home if China sends a vessel to pick them up, it said.

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.

Keywords: Diplomatic spat

More In: International | News