One person has been shot dead and another wounded during a gun battle involving supporters of the armed occupation of a wildlife refuge in Oregon.
Ammon Bundy and five others were arrested during a traffic stop, police said. One person was injured.
Two other activists connected to the group were later arrested in separate incidents, also in Oregon.
The self-proclaimed militia led by Mr Bundy occupied the refuge earlier this month in support of two local ranchers.
Other members of the group were reportedly still at the refuge, where the FBI was setting up a perimeter.
FBI officials said in a statement Mr Bundy, 40, was arrested in a traffic stop on Highway 395 along with his brother Ryan Bundy, 43, Bryan Cavalier, 44, Shawna Cox, 59, and Ryan Walen Payne, 32.
Two other activists connected to the group, Joseph Donald O'Shaughnessy, 45, and Peter Santilli, 50, were later arrested, separately, in Burns, Oregon.
Each of the defendants faces a charge of conspiracy to impede officers of the United States from discharging their official duties through the use of force, intimidation, or threats, the FBI said.
According to the Oregonian newspaper, Mr Bundy was en route to a community meeting in John Day, Oregon, where he was scheduled to be a guest speaker, when authorities stopped his vehicle.
The newspaper said Ryan Bundy was injured in the arrest, suffering a minor gunshot wound. Authorities did not release the identity of the person killed.
About 40km of Highway 395 was shut in both directions following the incident, local officials said.
A joint statement released by the FBI and Oregon State Police said the two forces conducted an "enforcement action to bring into custody a number of individuals associated with the armed occupation of the Malheur National Wildlife Refuge. During that arrest, there were shots fired".
The statement added: "One individual who was a subject of a federal probable cause arrest is deceased. We will not be releasing any information about that person pending identification by the medical examiner's office.
"One individual suffered non-life threatening injuries and was transported to a local hospital for treatment. He was arrested and is currently in custody."
Mr Bundy and a right-wing militia group occupied the refuge on 2 January to protest against the imprisonment of two ranchers in rural Harney County.
My Bundy and his brother are sons of Clive Bundy, who was in 2014 involved in a stand-off over grazing rights between armed anti-government activists and federal officials.