Military authorities in South Korea and the U.S. are trying to identify the two missiles North Korea fired on Thursday following analysis that they traveled as far as some 690 kilometers.

Officials believe the transporter erector launcher(TEL) used in the latest launch is similar in shape with the one used in the KN-23 short-range missile launches carried out on May fourth and May ninth.

Seoul and Washington are open to the speculation the missiles launched on Thursday could be an entirely new type, as the two sides continue to identify their exact specification.

South Korea's Joint Chiefs of Staff said that more analysis is necessary.

Military experts say the missiles are likely the completed version of the KN-23 which is believed to be similar to the Russian Iskander missile.

One expert said the latest launch appeared to be done with the aim of improving missile performance.