"The remaining four were deployed at a front-line fleet and put into maritime operations today," the Navy said in a statement. It did not reveal the location, but a defense source said the new assets will operate near the tense western sea border between the two Koreas.

The twin-engine rotorcraft is armed with lightweight torpedoes, 12.7-mm machine guns and advanced anti-ship guided missiles.

It's also equipped with the dipping sonar system and AESA radar with the range of around 360 kilometers. It features a maximum endurance of 2 hours and 40 minutes.

"As the eight new AW-159 maritime operation helicopters with superb anti-submarine, anti-ship detection and attack capabilities have become fully operational, our military's defense posture has been strengthened further," said Cdr. Kwak Han-jung, commander of the Navy's 622th aviation unit.

In response to the North's growing submarine threats, the South's Navy plans to acquire a dozen more new anti-submarine warfare helicopters in a 900 billion-won ($782 million) program.

Leonardo Helicopters, the manufacturer of the AW-159, hopes for a repeat order. Other candidate models include Sikorsky's MH-60R and NHIndustries' NH-90. (Yonhap)