RALEIGH, North Carolina (Reuters) - Two men charged in North Carolina last month with plotting terrorist attacks overseas also planned to attack the U.S. Marine Corps base in Quantico, Virginia, authorities said on Thursday.

The two were among seven suspects arrested in August for conspiring to provide material support to terrorists and for conspiracy to murder, kidnap, maim and injure people overseas.

A new indictment unveiled on Thursday charged Daniel Patrick Boyd, the group’s alleged ringleader, and Hysen Sherifi “with conspiring to murder U.S. military personnel” in connection with the planned assault on the Marine Corps base, the U.S. Attorney’s Office in Raleigh said in a statement.

It offered no details, except to say that Boyd had undertaken reconnaissance of Quantico and obtained maps of the base in order to plan the attack.

The U.S. Attorney’s Office said Boyd also possessed armor piercing ammunition, and had stated that it was “to attack the Americans.”

“These additional charges hammer home the grim reality that today’s home-grown terrorists are not limiting their violent plans to locations overseas, but instead are willing to set their sights on American citizens and American targets, right here at home,” U.S. Attorney George E.B. Holding said.

All seven suspects in the North Carolina case were denied bail after a hearing in Raleigh last month at which prosecutors played FBI recordings as evidence that they had discussed waging “jihad” as part of a conspiracy to conduct attacks in foreign nations.

The United States has been on heightened security alert since the September 11 attacks in 2001 and authorities have publicized efforts to crush domestic terrorist cells before they have a chance to act.

Prosecutors have said Boyd trained in terrorist camps in Pakistan and Afghanistan from 1989 to 1992, and fought against the Soviets in Afghanistan.

Boyd is a U.S. citizen and Sherifi is a native of Kosovo and a legal permanent resident of the United States.