South Korea used machine guns in cracking down on Chinese boats illegally fishing in its waters off the western coast on Saturday but no casualties or damage was reported, government officials said.

South Korea's patrol boats fired 95 bullets at 11:16 a.m. in chasing off around 30 Chinese boats operating in waters off the western port city of Incheon, according to the Ministry of Public Safety and Security and the Coast Guard.

The Chinese vessels ignored warnings and continued the operation, with some strongly resisting the crackdown, they said.

The Coast Guard used the M60 machine guns in accordance with its operation manual, they added. 

No damage or casualties for the South Korean boats have been reported, but the Coast Guard has yet to confirm the damage of the Chinese boats as they fled.

The Coast Guard informed the incident to its counterpart in Beijing and asked for cooperation, according to the officials. 

Earlier this month, the Coast Guard fired 600-700 bullets from a ship-mounted M60 in the process of capturing two fishing boats operating illegally off the western port city. No injuries or damage were reported. China expressed strong displeasure with what it sees as a "violent" crackdown. 

Illegal fishing has been a sensitive diplomatic issue between the two countries in recent months. South Korea has toughened measures against illegal fishing in its waters since one of its patrol boats sank in October while pursuing Chinese vessels.  (Yonhap)