Japan said Thursday it had protested to Beijing that a Chinese trawler suspected of poaching off Japan's southern coast sailed away with Japanese inspectors on board. China disputed the boat had crossed the border to fish and said it was dissatisfied Japanese fisheries authorities went on board.

Chief Cabinet Secretary Yoshihide Suga said the boarding occurred Nov. 5 in Japan's exclusive economic zone off Kagoshima and Japan complained about the "vicious" case via diplomatic channels.

The incident surfaced more than 50 days after it occurred when Suga responded to a reporter's question following a news report. Suga did not explain why nothing was released earlier and the Foreign Ministry declined to give further details.

Fisheries officials said about 10 Japanese officials boarded the trawler for inspection in Japan's EEZ but the trawler kept sailing into intermediate waters.

The inspectors returned to their own ship after its half-day chase of the trawler, with the help of Japanese coast guard. They had to let the Chinese trawler go since it by then had escaped the EEZ, Japanese officials said.

In Beijing, a Chinese Foreign Ministry spokeswoman Hua Chunying told a news conference that Japan's accusation the Chinese boat had crossed the border to fish was "not true" and that China expressed strong dissatisfaction on the boarding check conducted by Japanese fishery authorities. She expressed hope that Japan respects Chinese fishermen's right to fish, demanding Japan "not interrupt (their) normal operation."

The number of suspected Chinese poachers has been rising in recent years, prompting Japanese fisheries officials to step up patrolling. Four Chinese boats were captured for illegal fishing off the Japanese coast last year, according to the agency statistics.