WASHINGTON - (AP) - The Obama administration is warning Americans about potential terrorist threats in Europe and urging U.S. citizens to be extra vigilant when they're in public places such as tourist spots and transportation hubs.

The State Department on Sunday came out with a travel alert for Europe that advises U.S. citizens living or traveling there to takemore precautions about their personal security. The alert is onestep below a formal travel warning advising Americans not to visitEurope.

U.S. and European security experts have been concerned for days that terrorists may be plotting attacks in Europe with assaultweapons on public places, similar to the deadly 2008 shooting spreein Mumbai, India.