On Aug. 14, the Japanese news agency Kyodo reported that the missiles were variants of the Soviet-origin Scud B ballistic missile. Kyodo, quoting a Western source, said the missiles were launched in southwestern Syria in late May.

"North Korea, Syria and Iran have test-fired new short-range ballistic Scud missiles they jointly developed," Kyodo said. "But the test in Syria in May resulted in failure."

Kyodo said one of the missiles veered off-course and landed in the Syrian town of Manbij near the border with Turkey. The report said more than 20 people were killed and 60 injured.

The second missile was said to have landed near the border with Iraq. There were no reports of injuries.

The sources said Iran has been financing a missile development program to upgrade the Scud B, with a range of 300 kilometers. They said the project, believed to have begun in 2007, was meant to enhance a Scud B variant with a modern guidance system.

Pyongyang was believed to have supplied the engine while Iran and Syria worked to improve the warhead and guidance systems. The sources said warhead and guidance technology was provided by China and Russia.

But another source said the May test was that of an enhanced model of the Scud D. Scud D, with a range of 700 kilometers, contained a separating warhead.

The sources identified several entities involved in the missile development. They included North Korea's Ryonhap-2 Trading Co., Syria's Scientific Studies Research Center and Iran's Islamic Revolutionary Guard Corps.

Iran has also been financing North Korea's Taepo Dong intermediate-range missile program, the sources said. They said Iranian military delegations have attended virtually all of the Taepo Dong tests over the last three years.