A group of militiamen on Saturday occupied the headquarters of a national wildlife refuge in Oregon in support of two brothers who are slated to report to prison on Monday on arson charges, the Oregonian newspaper reported.

"We're planning on staying here for years, absolutely," Ammon Bundy, one of the occupiers, told the newspaper via telephone.

Militia members at the refuge claimed to have as many as 150 supporters with them. The Malheur National Wildlife refuge building, federal property managed by the US Fish and Wildlife Service, was closed for the holiday weekend.

Bundy said that while the occupiers, who included his brother Ryan Bundy, were not looking to hurt anyone, they would not rule out violence if police tried to remove them, the Oregonian reported.

The occupation came shortly after a few hundred marchers paraded through Burns, Oregon, about 50 miles (80 km) away, to protest at the prosecution of father and son Harney County ranchers Dwight Hammond Jr. and Steven Hammond, who were ordered returned to prison by a federal court which ruled their original sentences were insufficient.

The Hammonds had served time after being convicted in 2012 of setting fires on public land to protect their property from wildfires.

"The facility has been the tool to do all the tyranny that has been placed upon the Hammonds," the Oregonian quoted Ammon Bundy as saying.

"This is not a decision we've made at the last minute," he added, calling on other militiamen to join them.

The Bundys are the sons of Nevada rancher Cliven Bundy. The Bundy family ranch in Bunkerville, Nevada, some 80 miles (130 km) northeast of Las Vegas, was the site of an armed protest against the US Bureau of Land Management in April 2014.

The stand-off gained nationwide attention as the agency sought to seize cattle because the elder Bundy refused to pay grazing fees. The federal agents ultimately backed down, citing safety concerns, and gave back hundreds of Bundy cattle which they had rounded up.