Truck owners and truck rental agencies in the U.S. must be “vigilant” about the increasing frequency of “ramming attacks” by terrorists using vehicles as killing machines, according to a new Transportation Security Administration report obtained exclusively by NBC News. The unclassified report warns owners, operators and rental agencies to protect their vehicles from theft. Entitled “Vehicle ramming attacks: Threat landscape, indicators and counter measures,” the report was sent Tuesday to local law enforcement agencies and private companies working with the Department of Homeland Security.

The report notes that in the past three years, at least 173 people have been killed and more than 700 wounded in 17 ramming attacks around the world. Of the 17 attacks, 13 resulted in fatalities. Five were carried out in France both before and after the Nice attack and four took place in Israel. Nine of the 17 attackers were carried out in the past 10 months. One involved an Ohio State University student who drove his car into a crowd last November, then began slashing fellow students before campus police killed him. Eleven people were wounded. READ MORE