"Having pieced together the South Korea-US analysis of the 'underwater nuclear attack drone' as well as expert views on it, our military is putting weight to the possibility that the claim might have been exaggerated or fabricated," the JCS was quoted as saying by the korean news agency.
The South Korean military assessed North Korea's new weapon amid growing concerns that Seoul and Washington might be incapable of opposing Pyongyang's capabilities.
"There have been movements indicating the North has been working to develop an unmanned undersea vehicle, but our assessment is that it is still at an early (development) stage," the JCS said, according to the news agency.
On March 24, the state-run North Korean Central News Agency (KCNA) reported that the country had tested the Haeil underwater drone, designed to carry nuclear weapons and capable of creating radioactive tsunamis by underwater explosions. According to the report, the drone had traveled 362-492 feet (80-150 meters) below the surface of the Sea of Japan for over 59 hours. Pyongyang also confirmed the testing of two Hwasal-1 and two Hwasal-2 strategic cruise missiles which were equipped with warheads simulating nuclear ones.