The recent terror attack at a Christmas market in Berlin that killed 12 people has caused countries such as the United States to increase its securities in several major cities. But not all countries are at risk from terror attacks as Japan and Switzerland, among others, are considered safe.

The Daily Mail reports that U.S. cities such as New York, Chicago, and Boston will have increased police presence following the deliberate attack of a man in a Christmas market in Germany's capital that left 12 people dead and 48 more injured. The man is believed to have hijacked a 25-tonne lorry, which he used to kill the people and injure others.

The NYPD said that they already deployed highly trained teams to high-profile locations in New York City, such as the Winter Village market in Bryant Park and the Christmas market near Columbus Circle. In Chicago, police said they will increase their presence in downtown Chicago, where an annual Christmas market in an outdoor plaza is being held.

Boston Mayor Martin J. Walsh said they will be putting barriers around City Hall Plaza in an attempt to protect the "Boston Winter" holiday market. The city already experienced a terror attack three years ago when terrorist bombed the Boston Marathon in April 2013, killing three people.

The U.S. is not the only city that's on high alert as countries such as the United Kingdom, France, Turkey, and Belgium also has a high threat of terror attack, according to The Telegraph. Paris was not new to terror attacks as last July a truck was driven through a crowd of people walking along a promenade in Nice. The terror attack killed 84 people and injured more.

The U.S. has actually issued a travel warning last November for its citizens to take precautions when traveling to Europe for the holiday season. This is due to information that "the Islamic State of Iraq and the Levant (ISIL or Da'esh), al-Qa'ida, and their affiliates continue to plan terrorist attacks in Europe."

Of course, not all countries are at high risk from terror attacks as Japan and Switzerland, along with Iceland and Poland are countries that are considered to have a low risk from terror threat. Tourists who are traveling to Bolivia, Ecuador, Hungary, the Czech Republic, and Vietnam also don't have to worry about terror attacks as these countries also have low terror threat.

With the threat of terror attacks at an all-time high this season, it's important for people to be vigilant and careful. It's also advisable to try and avoid large crowded areas, especially popular landmarks, and outdoor markets, as these are prime targets for terror attacks.