SEOUL: The South Korean navy fired warning shots on Tuesday at a Chinese patrol boat that crossed the disputed maritime border between South and North Korea, military officials in Seoul said.

A statement from the Joint Chiefs of Staff said the action was taken after the initially unidentified vessel encroached on South Korean territorial waters.

"It retreated as the warning shots were being fired," the statement said.

The Defence Ministry said the vessel was initially assumed to be North Korean.

Naval patrol boats from the North regularly test the boundaries of the Yellow Sea border which has been a military flashpoint between the two Koreas for decades.

"But it actually turned out to be a Chinese patrol boat cracking down on illegal Chinese fishing vessels," a ministry official told AFP.

Seoul has been asking Beijing to take a tougher stand on Chinese vessels that have been entering South Korean waters in increasing numbers to sate growing demand at home for fresh seafood.

Small, wooden Chinese ships were once tolerated in an area where the top priority has always been guarding against potential incursions from North Korea.

But in recent years, the small boats have given way to larger steel trawlers who engage in bottom trawling - dragging a large, weighted net across the sea floor that sweeps up everything in its path.

Around 2,200 Chinese vessels have been stopped and fined by South Korea for illegal fishing in the past four years, and the number of arrested fishermen jumped from two in 2010 to 66 in 2013.

There have been numerous cases of violent clashes between Chinese crews and South Korean coastguard trying to board their boats.

Pyongyang does not recognise the Yellow Sea border that was unilaterally drawn by US-led UN forces at the end of the 1950-53 Korean War.

The boundary was the scene of deadly naval clashes between the two Koreas in 1999, 2002 and 2009.

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