Twenty Syrian civilians were killed and 60 more were injured after a Scud missile test-fired jointly by Syria, North Korea and Iran in late May strayed off course, Japan's Kyodo News reported.

The launch was an attempt to test a new short-range ballistic Scud missile jointly developed by the three countries that they meant to replace an outdated version, according to the Japanese report, which quoted Western diplomatic sources.

A technical malfunction caused one of the two missiles test-fired to land in a market located in a town on the Syria-Turkey border, killing 20 and injuring 60 more.

Syrian military officials blocked off access to the area to recover what was left of the missile, Kyodo News reported, and told residents there had been a gas explosion.

The other missile may have landed in a border area between Syria and Iraq, the diplomatic source told Kyodo.

Kyodo also quoted a Middle Eastern military source, who said a problem with the missiles' guidance systems caused them to go astray.