Gun-toting protesters remained holed up in a federal wildlife refuge in Oregon on Monday night even though the two men whose prison sentences sparked their action turned themselves in to authorities and repudiated the protest.POLL: Do you support the Armed Takeover in OR?

The protesters said they wouldn't budge until the government addresses their demands, but the FBI said it was hoping to bring a "peaceful" end to the standoff at the remote Malheur National Wildlife Refuge.

"We feel we have exhausted all prudent measures and have been ignored," said Ammon Bundy, co-leader of the self-styled Citizens for Constitutional Freedom, who said the group wants the federal government to "remove its unlawful presence in this county."

Bundy's group seized the government property after splintering off from a larger protest about ranchers' rights in the small town of Burns.

The initial protest in Burns was in support of Dwight Hammond, 73, and his son Steven, 46, who faced more jail time for setting fires that spread to government land after their initial sentences were extended by about four years each.

The Hammonds surrendered Monday at the federal prison in San Pedro, California. Their lawyers said they plan to appeal to President Barack Obama for executive clemency.

Late Monday night, Bundy reinforced his message on Twitter:

But the ranchers distanced themselves from the protesters, and their lawyer told police that "neither Ammon Bundy nor anyone within his group/organization speak for the Hammond family."

Harney County Sheriff David Ward directly addressed those at the refuge during a news conference Monday, telling them: "It's time for you to leave our community, go home to your families and leave this community peacefully."

"You said you were here to help the citizens of Harney County," Ward said. "That help ended when that protest became an armed occupation."

Ward said in a separate video message Monday that that he was "very proud of the citizens of Harney County in the way that they've stood up to this."

No government employees were at the site at the time b ecause of the holidays. It wasn't clear how many people had occupied the building, but those inside have asked for others to join them in several videos posted online.

Related: Meet Ammon and Ryan Bundy, the Activists Leading the Oregon Standoff

The ringleaders are Ammon and Ryan Bundy — sons of Cliven Bundy, the Nevada rancher known for another standoff with the federal gove... in 2014.

The FBI said in a statement Sunday that it was working with local and state police "to bring a peaceful resolution to the situation."

The agency said it wouldn't be providing details of its response because of "safety considerations for both those inside the refuge as well as the law enforcement officers involved."