Oregon militia
A man breaks up a scuffle between a supporter and an opponent of the militia occupation during protests in Burn, Oregon, in early February Reuters

In a remarkable scene with audio streamed live online, FBI agents moved armoured vehicles into place to surround a camp where the last Oregon militia members were holed up in a federal wildlife refuge. But agents held back from a final confrontation to arrest the three men and a woman during the tense stand-off.

The armoured trucks were moved into position after the most volatile militia member, 27-year-old David Fry, drove an all-terrain vehicle outside of the encampment, then sped back after an agent approached him. Agents spent hours demanding the occupiers put down their weapons and surrender. No shots were fired, but tension mounted as Fry ranted about not being taken alive.

By late night, the militia members had agreed to surrender at a checkpoint outside of the camp once Nevada state Assemblywoman Michele Fiore and evangelist Franklin Graham arrived, the Oregonian reported.

Cliven Bundy, father of arrested militia leader Ammon Bundy, also had plans to arrive at the checkpoint.

The phone feed that broadcast the confrontation online ended at 10 pm as the militia members settled down for the night.

The stand-off played out for hours through an open phone line streamed to YouTube. At one point, an estimated 60,000 people listened as the occupiers screamed at the FBI agents and prayed with those on the phone.

At points, a law enforcement official can be heard demanding: "Come out with your hands up." Another shouts: "There's no place for you to go."

The four are the last of more than a dozen militants who stormed the federal building at the Malheur Wildlife Refuge at the start of January. They're protesting management of federal grazing lands, and want the territory turned over to ranchers.

Most of the occupiers surrendered or were arrested soon after police shot dead outspoken member LaVoy Finicum in late January during a confrontation on a roadway outside the encampment.

The four holdouts all face arrest on federal conspiracy charges for their role in the occupation.