Several American military bases in Europe have increased their alertness over the weekend, report American media.
According to the American military, there is a risk of a terrorist attack directed against American military personnel or military installations, according to CNN.
Several bases, including the US European Command's headquarters in Stuttgart, Germany, raised their alert level to "Charlie", the second-highest on the scale, on Sunday.
According to a military official who CNN has spoken to, the American military has not seen this threat level "in at least ten years" and that it usually means the military has received an "active and tangible threat."
