Authorities in a district of Battambang province threatened protesting fisherman Thursday, after they complained of illegal fishing methods along the Tonle Sap River.

Villagers say their fishing grounds are being destroyed by an illegal method of fishing that wipes out fish populations.

When they gathered to protest in Battambang, authorities threatened to sue them for defamation, according to rights groups, who say they are investigating further.

"The authorities said they knew every single villager who filed their complaints," said Chhor Saly, a representative of the villagers. "They said those villagers risked being sued on defamation. Not only did the authorities fail to resolve the complaint, they also threatened the villagers."

Yim Mengly, a rights investigator for Adhoc, said up to 90 percent of the villagers relied on fishing for sustenance and to earn a living.

"The villagers are not allowed to fish near the site where illegal fishing is done," he said. "In some cases their simple instruments were destroyed."