North Korea would need several more years to operationally deploy a recently tested new submarine-launched ballistic missile, the chief of South Korea's defense development agency said Monday.

Last week, North Korea claimed to have successfully conducted a test-firing of what it claimed was its "new-type SLBM Pukguksong-3" missile from waters off its eastern coast town of Wonsan, according to the North's Korean Central News Agency. 

"It was the first time that the new version was test-launched, and just a single firing cannot lead to operational deployment as its stability cannot be guaranteed," Nam Se-gyu, president of the Agency for Defense Development (ADD) said during a parliamentary audit.

"It would take several years" before operational deployment, he said, though he added that the North may speed up the process and put it into operation faster than expected.

Asked about the features of the new SLBM, the agency chief said it appears to be "a totally different one" from the previous version, the Pukguksong-1 missile, noting that its flight range appears to have been extended around 50 percent.

During last week's test, the missile flew around 450 kilometers at a maximum altitude of about 910 km, according to Seoul's Joint Chiefs of Staff. As Pyongyang said the missile was fired "in vertical mode," it would have flown a much longer distance if it had been fired at a normal angle.

North Korea did not provide its details, but experts have said that the Pukguksong-3 missile is presumed to have a flight range of 2,000 km or longer. The Pukguksong-1 SLBM and the Pukguksong-2 ground-based missile have flight ranges of around 1,300 km. (Yonhap)