Two protesters have been tasered and 23 arrested after clashes broke out with authorities as police moved into the Dale Farm site in Essex, where a planned eviction is underway.
Many of those trying to stop the eviction wore scarves to cover their faces, while residents and protesters attached themselves to objects within the site using bicycle locks and chains.
As night fell bailiffs and police continud to work on removing the barricades, but a spokesperson for Basildon council said they would not attempt to evict residents until the morning.
"There won't be an attempt to ask travellers to leave the site over night ," he said.
Officers in riot gear entered the site after breaking down a rear fence just after 7am, prompting angry confrontations. The move came as police and bailiffs held discussions, described by supporters as a distraction, at the main gate.
Police captured around half the site within minutes of the first charge and claimed to have secured the entire site by mid-day.
Speaking at a press conference on the site, Trevor Roe from Essex police said the use of tasers was an "isolated incident".
"Serious violence was offered to a pair of officers in particular, their response was to protect themselves," he said.
John Barron, the local MP, said the police had to take the action as protesters were "threatening violence with iron bars" and said the eviction was necessary to uphold the law.
"It's unfortunate that some protesters have resorted to violence. The police were right to take control of the site's clearance," he said.
"From what I have seen, the police have acted fairly and responsibly. Don't forget some protesters were throwing rocks, carrying iron bars and threatening violence.
"The police have been restrained but at the end of the day, the police have got to defend themselves to ensure there is no violence."
Environment secretary Caroline Spelman said the travellers had broken the law by refusing to vacate the land.
She told the BBC's Daily Politics: "Everybody knows you can't just occupy a piece of greenbelt land, rip off the turf and build what you want on it. You have to have planning permission."
Electricity supplies have been cut to the site. Supporters say this has turned off crucial medical equipment belonging to elderly residents. But the council has said generators are available to run equipment if needed.
One of the supporters of the Dale Farm residents set fire to a caravan in protest. "This is the persecution of a blood line," she told Sky News.
Tony Ball, the Basildon Council leader, said he did not take "any satisfaction" from the morning’s events.
"When I became a councillor, it was never in my mind and never did I want to preside over an operation where we saw police on the streets of Basildon," he said.
"But I am absolutely clear that after 10 years of negotiation to try and find a peaceful solution to this that actually what we are doing is the right thing.
"I think we have seen from the level of violence put up by the protesters this morning that it was absolutely right that the police led the operation.
“These are utterly disgraceful scenes and demonstrate the fact some so called supporters were always intent on violence."
Resident Nora Egan said she was struck as she told police they were not entitled to break down fences, which are legal. She said: "This is being led by the police, there is no sign of bailiffs."
Margaret Sheridan, another resident, also claimed she was injured. "They're rough and there is no reasoning with them."
The operation to remove the travellers from the site has been estimated to be in excess of £18 million.
Barron defended the cost of the operation. "People would say what price law and order if we didn't take this action, it's a matter of principle."
Ahead of today's eviction Amnesty International UK warned that just because Basildon Council had been told they could go ahead with the eviction, it did not mean they should.
Kate Allen, Amnesty's director, said: "Human rights law is clear that the council must not forcibly evict a community, without offering them an appropriate alternative. They have not done so.
“A forced eviction which violates international law and standards and calls the UK’s standing on human rights into question can, and must, be avoided.”