KUWAIT CITY -- Shots were fired from two unidentified civilian vehicles at U.S. troops near a northern Kuwait training area on Monday morning, causing no injuries, the U.S. Embassy in Kuwait said.

"Shots were fired from two unidentified civilian sports utility vehicles at United States military units near a northern Kuwait training area today," the U.S. Embassy said in a statement.

"The incident was reported to occur at approximately 7:50 A.M.

(0450 GMT). The U.S. military units did not return fire: the units reported no injury," the embassy said as quoted by AFP.

The Kuwaiti Defense Ministry and the U.S. military, in cooperation with the Interior Ministry, are conducting a joint investigation, it added.

U.S. troops are currently engaged in joint maneuvers in the northern Kuwaiti desert codenamed Operation Desert Spring.

Monday's was the third shooting incident in less than a week involving U.S. forces in Kuwait.

Last Tuesday a U.S. marine was killed and another injured when attacked by two Kuwaitis while conducting wargames on Failaka Island, 20 kilometers (12 miles) east of Kuwait City.

The two assailants were also gunned dowm.

On Wednesday, U.S. forces opened fire on a vehicle whose occupants "drew a weapon and pointed it at" U.S. troops in a Humvee all-terrain vehicle who were heading to their training area north of Kuwait City.

Fifteen Kuwaitis were arrested in connection with the Failaka attack and were referred to the public prosecution.

Interior Minister Mohammad Khaled al-Sabah said the suspects -- all Kuwaitis -- formed an "organization" that was planning to strike at five other U.S. and foreign targets.

A team from the U.S. Federal Bureau of Investigation is currently in the emirate following up on the attack and probing possible security lapses.