The South Korean military fired warning shots at a military vessel from the North that crossed their maritime border early today, a news report said.

The boat crossed the disputed boundary around 6.55am local time (5.55am Malaysian time) in the Yellow Sea, to the west of the peninsula, before retreating 20 minutes later after the South's navy fired five warning rounds, an unnamed Seoul military official was quoted as saying by the Yonhap News Agency .

North Korean vessels frequently cross the Northern Limit Line, which Pyongyang argues should be further south.

Tensions are high between the two Koreas, which remain technically at war after the 1950-53 conflict ended in a ceasefire and remains without a peace treaty.

In January, Pyongyang carried out its latest nuclear test explosion, and yesterday it launched a ballistic missile.

The UN Security Council vowed to "expeditiously" pursue "further significant measures" against North Korea in response to the launch, which Pyongyang said was carrying a satellite, but the council condemned it as a missile test.

- dpa