Gunmen in two civilian vehicles have fired shots at U.S. troops engaged in joint training exercises in Kuwait.

The U.S. embassy in Kuwait has issued a statement saying the shots were fired from two civilian sport utility vehicles at U.S. military units training in northern Kuwait.

According to the embassy, the soldiers did not return fire and there were no injuries. The Kuwaiti Ministries of Defense and the Interior, and the U.S. military are conducting a joint investigation.

Last Tuesday, a U.S. Marine was killed and another wounded in an attack during military exercises on a Kuwaiti island. Marines killed the two attackers, who were later found to have trained in al-Qaida camps in Afghanistan. Kuwait authorities rounded up dozens of suspects following the attack.

One day later a U.S. soldier fired a single bullet at a car, apparently believing he was under threat. That incident occurred as troops were moving to a desert training area near the Iraq border. No one was injured in that incident.