Large-scale clashes between police and travellers are expected today as teams of bailiffs begin evicting residents from the UK's largest illegal site at Dale Farm in Essex.

Around 80 families will be kicked off the six-acre site, a former scrapyard. But many of the travellers have put up barricades to keep the bailiffs out, and some activists have reportedly chained themselves to the makeshift barriers – built with bricks, barbed wire and car tyres – in support of the travellers.

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Riot-trained police are expected to preside over the operation and ensure that the eviction is carried out peacefully.

Residents are claiming their human rights are being breached because they have nowhere else to go. Their supporters include the United Nations and Amnesty International.

Nevertheless, last month a High Court judge backed Basildon Council and local residents over their calls for eviction.

Tony Ball, leader of Basildon council, expressed concern that the mounting tension at the site could prove dangerous.

He told reporters: "We wanted to keep residents updated about the operation. We now have no line of communication. We are very concerned that tension has increased and it may now make our job of clearing the site in a safe and orderly manner more difficult."