South Korea’s Joint Chiefs of Staff on Monday said in a preliminary analysis it found North Korea’s claims of the capabilities of its new strategic cruise missiles to be exaggerated.

The South Korean military detected North Korea launching cruise missiles at around 8 a.m. Sunday toward waters near the port city of Sinpo, South Hamgyong Province, the home to a North Korean base for submarines.

“We are looking into the possibility that the flight time claimed by North Korea may have been exaggerated,” Lee Sung-joon, the JCS spokesperson, told reporters at a briefing. He added that South Korea and the US intelligence authorities were undertaking a further analysis into the performance of the cruise missiles.

The North's official Korean Central News Agency said Monday that its leader Kim Jong-un supervised the test launches of the new cruise missiles built to be fired from submarines.

According to the KCNA, the two missiles were fired from the coast of Sinpo and each flew for over two hours -- 7,421 seconds and 7,445 seconds, respectively -- over the water before hitting their targets. The KCNA said Kim “expressed profound satisfaction” over the tests.

The JCS said the missiles appear to have traveled for a shorter time than that disclosed by the KCNA. Analysis to date could not confirm whether the missiles were fired using solid fuel.

The South Korean military is wary of the possibility of North Korea conducting tests of missiles using solid-fuel engines. Missiles using solid fuel can be launched more quickly than those using liquid fuel, making them harder to detect.

Sunday's launch came just four days after North Korea fired its Pulhwasal-3-31 cruise missiles, which are speculated as capable of carrying nuclear warheads.