Ammon Bundy and a group of armed supporters, including his brother Ryan, took over the an Ore. wildlife refuge over the weekend. Here's a look at the Bundy family's history of anti-government actions. (Jenny Starrs/The Washington Post)

An unpredictable new chapter in the wars over federal land use in the West unfolded Sunday after a group of armed activists split off from an earlier protest march and occupied part of a national wildlife refuge in remote southeastern Oregon.

The activists, led by rancher Ammon Bundy, set themselves up in the Malheur National Wildlife Refuge 30 miles southeast of here, defying the organizers of a rally and march held Saturday in support of two local ranchers who are scheduled to report to federal prison Monday to serve a sentence for arson.

Some of the occupiers said they planned to stay indefinitely. Harney County Sheriff David M. Ward said authorities from several law enforcement organizations were monitoring the situation.

“These men came to Harney County claiming to be part of militia groups supporting local ranchers,” Ward said in a statement Sunday. “When in reality these men had alternative motives, to attempt to overthrow the county and federal government in hopes to spark a movement across the United States.”

The occupation revealed deep divides among some Western ranchers who want freer rein over federal lands but are split on whether to achieve those goals peacefully or more confrontationally.

What we know about the occupied federal building in rural Oregon

Organizers of Saturday’s rally said several hundred protesters marched through Burns, a ranching town of fewer than 3,000 residents, in a show of support for Dwight Hammond, 73, and his son Steven Hammond, 46, who after decades of clashes with the federal government were sentenced in October to five years in prison.

But, at the rally’s end, Ammon Bundy and an estimated dozen supporters declared they would take up arms and occupy a federal refuge building in protest. Amanda Peacher, a reporter for Oregon Public Broadcasting, reported that the men had entered a building at the refuge that was unstaffed over the weekend.

“We’re out here because the people have been abused long enough, their lands and their resources have been taken from them to the point that it is putting them literally into poverty,” Ammon Bundy, clad in a brown rancher hat and thick flannel coat, told reporters Sunday morning, his breath forming small puffs of cloud in front of him as it hit the cold Oregon air.

Talking to reporters gathered at the entrance to the refuge property, Bundy said his group had not heard from law enforcement since taking over the un­occupied site and urged other citizens from across the country to join their effort.

Snowdrifts and miles of desolate highway studded with sagebrush and tumbleweed separate Burns, near the refuge, from Boise, Idaho, the nearest big city, which is about 220 miles to the east. Regulars at the Oasis, a restaurant in Juntura, Ore., said groups of travelers coming from Idaho had been stopping for food and gas on the way to Burns, where they hoped to lend support to the protesters. They didn’t want to talk about it too much. The subject is too sensitive, they said.

If a standoff resulting in violence occurs, Bundy said, it would begin on the government’s side.

“This refuge here is rightfully owned by the people, and we intend to use it,” he said, adding that they plan to assist ranchers, loggers, hunters and campers who want to use the land. “We will be here as a unified body of people that understand the principles of the Constitution.”

Prosecutors accused the Hammonds of committing arson on federal land in 2001 and 2006. The men and their attorneys argued that the fires had been set on their own property — once to prevent the spread of an invasive species of plant and once in an attempt to prevent the spread of a wildfire — and had accidentally burned onto public lands. But prosecutors said the fires were set in an attempt to destroy evidence that the Hammonds had been illegally hunting deer on the federal lands.

The two men have previously served prison time for the crimes, but late last year a federal appeals court concluded that their initial sentences had been too short — arson on federal property carries a mandatory minimum sentence of five years — and ordered the men back to prison. They have said they expect to report to authorities and have not commented on the armed occupation.

The occupation of the wildlife refuge comes at the conclusion of a lively weekend for an otherwise sleepy stretch of southeast Oregon.

For their supporters, the Hammonds represent the latest battle in a struggle as old as the American settlement of the West: pitting poor cattle farmers against the federal government and its land regulations in states such as Oregon, where the federal government owns more than half of the land.

“Most Americans, if they knew the story of the threats and the charges brought against these ranchers, they would say this isn’t right,” said Jeff Roberts, one of the organizers of Saturday’s rally. “We really wanted to show the family support and let them know that they’re not alone. That Americans don’t turn their backs on them.”

But there is a stark divide over how to best address the concerns of the cattle rancher. Some activists, like Roberts, believe the battle will be won through a deliberate public awareness campaign, rallies and town hall meetings.

Others have another tactic in mind: armed resistance.

The Bundy family, led by patriarch Cliven Bundy, is perhaps the best known of the anti-government groups arguing that expanding environmental and land regulation has unconstitutionally infringed on their rights and that armed confrontation is necessary to curb the federal overreach.

A 20-year clash between Cliven Bundy and federal authorities in Nevada came to a head in 2014, after the rancher threatened to shoot any federal agent who attempted to remove any of his cattle that officials say were illegally grazing on public land.

The standoff briefly made Cliven Bundy a conservative darling, and it ended when officials with the U.S. Bureau of Land Management opted to stand down and allow Bundy to continue to graze on the federal land.

“When the federal government was stopped from enforcing the law at gunpoint, that energized this entire movement,” said Heidi Beirich of the Southern Poverty Law Center, who said that Bundy’s success has fueled a renewed rise in the number of anti-government activist groups and self-described militias. “When you have a big win like they did at the Bundy Ranch, it emboldens people. . . . It is definitely a recipe for disaster.”

Holley and Lowery reported from Washington.