Seoul says it is lodging a formal complaint with Beijing accusing Chinese fishing boats of ramming and sinking a South Korean coast guard vessel.

South Korea's Foreign Ministry said Monday it had summoned a senior Chinese diplomat and complained about the sinking last Friday.

Seoul says the incident happened when the coast guard vessel was trying to stop Chinese fishing boats from suspected illegal fishing off South Korea's west coast. No causalities or injuries have been reported.

South Korean media reports said coast guard officers fired shots at the Chinese fishing boats as they approached the South Korean vessel.

The coast guard confirms that warning shots were fired into the sky, but says it does not know if any were fired at the Chinese boats.