BEIJING — China on Monday called on Malaysia to "fairly investigate" the cases of Chinese fishermen held for allegedly operating illegally in Malaysian waters.

China has sent personnel to visit detained crew members from six boats seized on Friday and provide them with personal protective equipment and other assistance, foreign ministry spokesperson Zhao Lijian told reporters.

"We have requested that the Malaysian side fairly investigate the case in accordance with law, protect the lawful rights and interests of the Chinese citizens involved and report the progress of the investigation in a timely manner," Zhao said at a daily briefing.

Malaysia is among the countries exercising overlapping claims with China to territory and resources in the South China Sea and has sought to clamp down on Chinese illegal fishing.

China claims virtually the entire strategic waterway, home to rich but overstressed fishing stocks and a potential wealth of mineral resources, as its own.

Malaysian officials said 60 Chinese crew members were arrested for lacking permits and anchoring illegally at two separate locations on Friday morning after a tip-off. They face fines and potential jail terms.