Families fighting eviction from the UK's biggest illegal traveller site were manning "barricades" after an appeal court ruling left them at the "end of the road".
Residents of the Dale Farm site near Basildon, Essex, said they had gone into "lockdown" and were preparing to "fight off the bailiffs".
A Court of Appeal judge refused travellers permission to continue their legal fight against Basildon Council.
Lord Justice Sullivan said there was no evidence likely to persuade appeal judges that the council's decision to enforce eviction notices was "unlawful". Lawyers representing the council said officials were making preparations to take action at the site, said to contain more than 80 families on 50 plots.
A spokeswoman for support group Dale Farm Solidarity said residents and supporters had gone into "lockdown" in "anticipation of an eviction".
"Today the Dale Farm community were rejected the right to appeal," said the spokeswoman. "In response to this news, residents of Dale Farm and their supporters reinforced the perimeter of the 50 plots, which house 83 families, and placed the entire site into lockdown in order to resist eviction."
Dale Farm resident Kathleen McCarthy added: "The barricades are all that stand between us and homelessness now... We'll have to fight off the bailiffs."
Candy Sheridan, vice-chair of the Gypsy Council and an adviser to the Dale Farm travellers, said of Lord Justice Sullivan's ruling: "It seems like the end of the road."
Basildon Council's Conservative leader Tony Ball said Dale Farm residents had been "living on borrowed time" and urged them to leave "peacefully and in a safe and orderly fashion".
He said evictions would take place as a "at a time of (the council's) choosing" and added: "Our job is now to clear this site in a safe and dignified manner and this is what we intend to do."