A standoff at a remote US wildlife centre in Oregon rolled into a fourth day yesterday with self-styled militiamen vowing to press on with the protest against the US government. Saturday's takeover of the Malheur National Wildlife Refuge outside the town of Burns, Oregon, was spurred by the imprisonment of two ranchers for setting fires that spread to federal land.The occupation marked the latest protest over federal management of public land in the west, long seen by political conservatives in the region as an intrusion on individual freedom and property rights.Protest leader Ammon Bundy, whose father's ranch in Nevada was the scene of an armed standoff against federal land managers in 2014, said his group was defending the constitution and personal liberty against the federal government.A Twitter page under Bundy's name said the group had no intention of leaving the refuge until its conditions were met.The protesters have said they aim to protect the rights of ranchers and start a national debate about states' rights and federal land-use policy that they hope will force the federal government to release tracts of western land.The FBI said it was working with law enforcement for a peaceful resolution and federal law enforcement officials have kept their distance from the wildlife refuge, which is closed to visitors. They are following US policy guidelines to prevent such standoffs from turning deadly as they did in Ruby Ridge, Idaho, and Waco, Texas, in the early 1990s. ..