BEIJING - China on Monday demanded that South Korea must not resort to force during its law enforcement process, saying it would keep a close eye on its detention of three Chinese fishing boats and their crews.

Seoul arrested 31 Chinese fishermen and seized three Chinese fishing vessels on Saturday after the boats "crossed into South Korea's exclusive economic zone for illegal fishing".

Foreign Ministry spokeswoman Jiang Yu said the Chinese Consulate-General in Kwangiu, the sixth-largest city in South Korea, is currently dealing with the incident.

"We urge the South Korean side to properly handle the relevant issues, and avoid using force while executing the law, to safeguard the Chinese fishermen's legal rights and interests," Jiang told the ministry's regular media briefing on Tuesday.

Reports quoted local police as saying they fired tear gas and flares at the Chinese fishermen, who resisted detention by using shovels and sticks.

It is said that the 31 Chinese crewmembers are likely to face charges of obstructing the performance of official duties.

According to the China-South Korea Fishery Agreement, the law enforcement departments of the two countries administer their respective fishing boats, and report to each other about the illegal activities but have no right to board the fishing boat of the other country to enforce the law.

A similar incident happened in December 2010 when one Chinese crew member was killed when a 63-ton Chinese fishing boat capsized after ramming into a 3,000-ton South Korean coastguard ship.