Fears of a bloody stand-off at Dale Farm are growing as a number of extreme anarchist groups sign up to resist the eviction.

Police fear as many as 1,000 people from up to 30 anarchist groups plan to descend on the illegal Crays Hill site, near Billericay.

Chief Supt Tim Stokes, who is leading police involvement in the eviction, said: “What is beginning to change is there are groups coming from outside.

“We have intelligence a number of groups are inciting others to commit violence against the police. We have intelligence there will be 2,000 people in total on the site, with an extra 1,000 coming from outside.”

Police would not name any of the groups concerned, but the Echo understands radical groups pledging support to the families include the No Borders UK Network and No One is Illegal groups, which advocate no immigration controls in any countries, and Communities of Resistance, which wants to abolish prisons.

Members of UK Uncut, some of whose members occupied Fort-num and Mason, in Piccadilly, in March, as violent groups split from a peaceful march against Government cuts, are also doing call outs for activists.

However, in response many members posted on Facebook they did not support the travellers.

Police are now actively monitoring social networking sites and other websites and will deal “robustly” with anyone inciting violence.

Other groups such as Dale Farm Solidarity, which appears to be manning Camp Constant, where protesters are staying, maintain they will take part only in passive resistance, such as a human shield and obstructing bulldozers.

Campaigners at the site include anti-nuclear demonstrators, such as Suffolk-based Ziggy Norton, who held a banner outside court on Wednesday, saying “no ethnic cleansing” at Dale Farm.

Tyres, which could be torched and even concrete barrels for people to chain themselves to, are understood to have been moved on to the site, alongside barbed wire and gas canisters which have been stockpiled for several years.

The “worst case” cost of evicting families from the illegal site in Crays Hill soared to £18million, after police intelligence showed anarchists may hijack protests, as revealed by the Echo in March.

Len Gridley, 52, whose Oak Road home backs on to the site, said: “People have reported seeing canisters being buried on the site.

“The police moved the ones put up by the scaffolding, but there could be hundreds more ready to use around the site.”

The Echo contacted Dale Farm Solidarity to ask if it was doing anything to prevent anarchists taking part, but the group refused to comment. No arrests have been made yet in connection with the protests, because police do not have specific details on the anarchists.

Officers will be actively monitoring and gathering evidence of people inciting trouble, who are likely to be arrested in the run-up to the eviction.