Four men from California have been charged with plotting to kill Americans overseas and in the United States by joining al Qaida and the Taliban in Afghanistan.
FBI spokeswoman Laura Eimiller said they were under arrest for plotting to bomb government facilities and public places.
According to the federal complaint, unsealed during initial appearances, 34-year-old Sohiel Omar Kabir introduced two other California men to the radical Islamist doctrine of now-dead al Qaida leader Anwar al-Awlaki.
Authorities say Kabir traveled to Afghanistan and communicated with the two - Ralph Deleon, 23, and Miguel Alejandro Santana Vidriales, 21 - so he could arrange for their travel to join him and meet his contacts for terror organisations.
They later recruited 21-year-old Arifeen David Gojali, according to authorities.