Shafaq News/ The US military has placed several military bases across Europe on high alert over the weekend amid fears that a terrorist attack might target US personnel or military installations.

The US military has raised the alert level to Force Protection Condition "Charlie" at several bases across Europe, including the US Army garrison in Stuttgart, Germany, where US European Command is headquartered, officials said on Sunday, CNN reported.

That status "applies when an incident occurs or intelligence is received indicating some form of terrorist action or targeting against personnel or facilities is likely," according to the US Army.

CNN added, according to one of the US officials stationed at a base in Europe, they haven't seen this threat level "in at least ten years" and said it usually means the military has received an "active-reliable threat."

The spokesperson for US European Command, Cdr. Dan Day, told CNN that USEUCOM is "constantly assessing a variety of factors that play into the safety of the US military community abroad. As part of that effort, we often take additional steps to ensure the safety of our service members. For operational security reasons, we will not get into specific measures, but we remain vigilant."

Day added that "USEUCOM constantly monitors the security environment to ensure its personnel are informed and best postured to assure the safety of their individual person, family, and loved ones. As always, USEUCOM advises personnel in the European theater to remain vigilant and stay alert at all times," according to CNN.

It is not clear what intelligence triggered the heightened security, but European authorities have warned of a potential terror threat on the continent, especially ahead of the Paris Olympics in July and during the current European football championships in Germany.

CNN pointed out that the German government brought in 580 international police officers to assist with security alongside German officers. Interior Minister Nancy Faeser said ahead of the tournament, "We are preparing ourselves for all conceivable dangers: from Islamist terror to violent criminals and hooligans."

France has also prepared for the possibility of a potential terror threat to the Olympic Games, which begin in just under a month. Since March, France has raised its national security alert system to the highest level, according to the US embassy in France.

"French authorities actively monitor terrorist threats from organized groups and radicalized individuals," the embassy said. "Attacks may happen with little or no warning, targeting tourist locations, major sporting and cultural events, and other public areas that attract large numbers of civilians."