South Korean navy fires warning shots as Kim Jong-Un's boats cross into their territorial waters

North Korean boats crossed at the Yellow Sea boundary

A South Korean naval vessel fired ten warning shots at it

The ships then returned to the northern side

South Korea's navy has fired warning shots after three North Korean patrol boats crossed the maritime border into its territory, it was revealed today.

The North Korean boats crossed into the South Korean waters at the Yellow Sea boundary, known as Northern Limit Line, at around 4pm local time on Tuesday.

The ships returned to the northern side after a South Korean naval vessel fired ten warning shots, an official with the South Korean Defense Ministry said.

Tension: In the latest sign of rising animosity between the bitter rivals, South Korean officials said a North Korean vessel fired two artillery shells at one of its warships patrolling in the Yellow Sea (file image)

The NLL is the de facto maritime border, which stretches from the western coast of the peninsula into the Yellow Sea, marking the boundary between the two neighbors.

It was set by the United Nations following the Korean War but the North does not recognise it, CNN reported.



Incidents have been known to occur on and around the border, including one earlier this year when North and South Korean artillery batteries exchanged hundreds of shells.

In 2010, South Korea accused North Korea of using a submarine to torpedo the South Korean ship Cheonan, killing 46 sailors.

Lookout: A South Korean navy defense ship on patrol near Yeonpyeong Island (file picture)

Last week it was revealed satellite images showed two new North Korean frigates, the largest surface combat ships the nation's navy has constructed in a quarter-century, a North Korea-watching website.

The website, 38 North, says the frigates are designed to carry one helicopter each and appear to be designed to counter South Korean submarines and protect fisheries. The vessels appear to be equipped with anti-submarine rocket launchers.

The vessels can be seen in commercial satellite images from December and January. One is berthed at a shipyard in the west coast port of Nampo, other at a shipyard at the northeastern port of Nanjin.