Two of the three surface-to-air missiles North Korea fired off last week disappeared from the South Korean radar, the military said Tuesday, indicating that they may have malfunctioned.

The Joint Chiefs of Staff initially said Pyongyang fired one surface-to-air missile toward the East Sea on Friday but confirmed later that two more missiles were launched at that time.

But shortly after the launch, two of the missiles disappeared from the military's surveillance radar that was tracking the missiles' trajectories, JCS spokesman Jeon Ha-kyu said in a press briefing.

Missiles, when fired, move in a similar trajectory although in a failed launch they will go off course and crash before reaching their target.

"Two missiles disappeared from the radar in several seconds (after launch) and had a relatively short distance of flight," the spokesman said.

Asked to confirm whether it was a failed launch, he said the matter is "being analyzed."

North Korea's ballistic missile launches constitute a violation of United Nations Security Council resolutions, but the firing of surface-to-air missiles does not, the spokesman said in response to journalists' inquiry into why the JCS did not provide full information on North Korea's Friday launch at first. (Yonhap)