North Korea's 40m long Sango class submarine (photo : Yonhap)
SEOUL, (Yonhap) -- North Korea has strengthened the intensity of its naval drills this year by deploying a new submarine, prompting South Korea's military to raise its level of vigilance, a government source here said Wednesday.
"North Korea is on naval maneuvers near its bases off the East Sea and Yellow Sea by mobilizing five to six submarines, including a new Sango class submarine," the source said on the condition of anonymity.
"Our military is closely monitoring activities of the North Korean military because it is unusual for the North to strengthen the intensity of its submarine drills," the source said.
In addition to its rudimentary 35-meter-long Sango class submarines, the North recently put the new 40-meter-long Sango submarines into service, according to the source.
On Tuesday, Defense Minister Kim Kwan-jin told lawmakers that his military is carefully watching the eastern and western sea borders with North Korea as the North's armed forces have staged seaborne infiltration drills.
Tensions on the Korean Peninsula remain high following the North's two deadly military attacks last year, which killed a total of 50 South Koreans.
The South's military bolstered firepower and surveillance systems near the sea borders with North Korea to counter any possible attacks from the North.