Osama Bin Laden, leader of al Qaeda, who is purported to have approved the plans for attacks in Europe.

The U.S. State Department issued an alert yesterday, asking U.S. citizens to be vigilant in their travels throughout Europe. “Terrorists may elect to use a variety of means and weapons and target both official and private interests,” the statement read.

The State Department stopped short of issuing a “Travel Warning”, which would have warned Americans to avoid travelling to Europe.

In a meeting with reporters, Patrick Kennedy, an Under Secretary at the State Department, advised travelers to:

“…use common sense if they see unattended packages or they hear loud noises or they see something beginning to happen that they should quickly move away from them. These are common sense precautions that people ought to take – don’t have lots of baggage tags on your luggage that directly identify you as an American, know how to use the pay telephone, know how to contact the American embassy if you need help.”

“…avoid public demonstrations, avoid civil disturbances. Don’t discuss your travel plans or where you’re going with others or where others may overhear them. Know what you’re doing, be aware of your circumstances around you. If you see something that looks untoward, move away from it and inform law enforcement personnel. If you see unattended packages, or such, move away from them and inform law enforcement.”

While flights, mass transit systems, and tourist attractions, remain open and are operating on their normal schedules, travelers will likely experience an increased security presence. Security screenings may be more frequent and thorough.

Sky News, citing unnamed sources, is reporting that Pakistani militants are planning coordinated attacks on targets in Europe. Numerous reports are indicating that the U.S. has increased drone attacks on targets in remote areas of Pakistan, in an attempt to disrupt the plans.

ABC News has reported that the U.S. received word of the plans from a German terror suspect that was detained in Afghanistan. The suspect indicated that several teams of terrorists with European passports had been dispatched from camps in Waziristan and Pakistan. According to the suspect, the plan was approved by al Qaeda leader Osama Bin Laden.

Under Secretary Kennedy emphasized that the State Department is not asking Americans to avoid Europe at this time:

“…we’re not recommending, that American citizens of any kind – business, tourism, study abroad – we are not – we are not, not, not saying that they should defer travel to Europe at this time, absolutely not.”

Europe is the top foreign travel destination for Americans. 12 million Americans travelled to Europe in 2009, spending over $20 billion, according to the U.S. Department of Commerce.