South Korea’s coastguard has for the first time opened fire on Chinese fishing trawlers, which are increasingly straying into Seoul’s territorial waters amid growing Chinese demand for fresh seafood.

Tuesday’s incident comes less than a month after Seoul warned it would use a “more aggressive” firearms policy in encounters with illegal fishing vessels. This was prompted by the sinking of a 4.5-tonne Korean coastguard ship that was rammed while trying to intercept a trawler.

The coastguard seized two trawlers after firing about 700 M60 machine gun rounds at a fleet of 30 fishing ships South Korean authorities say had “rushed” its vessels. No one was killed or injured in the incident, which coastguard official Kim Jung-shik said was sparked by the threatening behaviour of the fishermen.