The four remaining protesters occupying a wildlife refuge in the US state of Oregon have been arrested "without incident", the FBI has said, ending an occupation that has lasted for 41 days.

FBI agents arrested the fourth man at 11am local time on Thursday, about two hours after the surrender of the other three protesters.

"No one was injured, and no shots were fired," the FBI said in a statement. "Agents arrested the remaining four occupiers as they walked out of the refuge to the FBI checkpoint."

The agents closed in on the group on Wednesday, saying that negotiations to end the standoff without violence were continuing.

The Los Angeles Times reported that the remaining protesters had said they intended to surrender while carrying American flags.

The four protesters were indicted last week, together with 12 others previously arrested on charges of conspiring to impede federal officers during the standoff at the compound.

  What will stop Oregon standoff?

The takeover at Malheur National Wildlife Reserve, which began on January 2, was sparked by the return to prison of two Oregon farmers convicted of setting fires that spread to federal property in the vicinity of the refuge.

The occupation, led by Ammon Bundy, was also directed as a protest against federal control over millions of acres of public land in western United States.

Bundy and 10 others were arrested in January in Oregon, most of them during a confrontation with the FBI and state police on a snow-covered roadside where a spokesman for the group, Robert "LaVoy" Finicum, was shot dead. A 12th member of the group turned himself in to police in Arizona.

READ MORE: Militia leader urges occupiers to leave Oregon refuge

The FBI said its agents moved to contain the four remaining protesters on Wednesday evening after one of the occupiers drove an all-terrain vehicle outside the barricades previously set up by the self-styled militia members at the refuge.

FBI agents attempted to approach the driver, and he sped away back to the compound, after which federal agents "moved to contain the remaining occupiers by placing agents at barricades both immediately ahead of and behind" their encampment, the FBI said.

A number of the occupiers were giving their version of events as they unfolded via an independent internet broadcast, "Revolution Radio", which is known to be sympathetic to the occupation.

One woman said FBI agents had moved to within 45 metres of the occupiers' position in the compound. One protester - identifying herself as Sandy Anderson - reported seeing FBI snipers posted on a nearby hillside with high-beam vehicle lights trained on the compound.

"If they tear gas us, it's the same as firing on us," she said, adding: "Don't come in. Don't do it."

An FBI statement said: "It has never been the FBI's desire to engage these armed occupiers in any way other than through dialogue, and to that end the FBI has negotiated with patience and restraint in an effort to resolve the situation peacefully." 

  Farmers speak out as Oregon armed group continues standoff

Source: Al Jazeera and agencies