The multi-million pound eviction of travellers on the Dale Farm site descended into violence today with two people Tasered and missiles thrown at police.
There were seven arrests after riot police entered the UK's largest illegal travellers' site in Essex to clear the way for bailiffs.
Around 50 officers were pelted with rocks and liquids as they broke down a rear fence to get in.
Protesters chanted: "F*** the police, no justice, no peace." They also set fire to a caravan placed across the street inside the site.
The eviction has begun after the travellers lost their final high court battle to stop Basildon Council going ahead with the clearance of illegal plots.
Tonight police had secured the area and removed protesters from a 40ft high scaffolding tower which had been erected at main gate to the site. It is being dismantled which officials hope should allow access for the bailiffs tomorrow to begin removing the plots.
But sporadic clashes between police and protesters were continuing tonight.
Electricity supplies were cut and supporters said this had turned off crucial medical equipment belonging to elderly residents.
Paramedics were escorted on to the site by supporters to treat resident Nora Egan, who claimed she suffered back injuries in a confrontation with police.
Essex Police said they would investigate the circumstances leading up to a woman receiving "a minor back injury".
Margaret Sheridan also claimed she was injured. "They're rough and there is no reasoning with them," she said.
Kathleen McCarthy, a Dale Farm resident, said: "The memory of Dale Farm will weigh heavily on Britain for generations - we are being dragged out of the only homes we have in this world.
"Our entire community is being ripped apart by Basildon Council and the politicians in Government."
An ambulance service spokesman said one resident had been taken to hospital and another was receiving treatment. Four others refused treatment.
Supporters said resident Cornelius Sheridan, who is in his 50s and seriously ill, was taken to hospital after the power supply to his defibrillator had been cut.
Superintendent Trevor Roe of Essex Police said: "The tactic was to take early control of the site. Where we have intelligence there is likely to be violence we need to protect members of the public including bailiffs, police officers, travellers and protesters from injury.
"We also needed to provide access for all emergency services should they need to enter and exit the site.
"Serious violence was offered to two officers and their response was to protect themselves by deploying Taser. Tasers are not generally deployed in public order situations but in this case the officers were threatened directly."
The seven people were arrested for offences including violent disorder and a breach of the peace.
Basildon Council leader Tony Ball condemned the violence.
He said: "When I became a councillor, it was never in my mind and never did I want to preside over an operation where we saw riot police on the streets of Basildon.
"But I am absolutely clear that after 10 years of negotiation to try and find a peaceful solution to this that actually what we're 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."
One evicted resident said: "I'm so angry and dismayed that people are actually doing this. The rest of the world is also persecuting people who choose to live differently from the so-called norm.
"They (police and bailiffs) shouldn't be doing it. What I'm hearing is that they are not being as gentle as they would like to believe. People have been pushed over and have hurt themselves."
Constituency Tory MP John Baron (Basildon and Billericay) said: "It's unfortunate that some protesters have resorted to violence. The police were right to take control of the site's clearance.
"The protesters were there at the request of the travellers and I urge the travellers now to ask the protesters to leave peacefully and lead by example and leave themselves.
"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."
It has been estimated that the cost of evicting residents could soar to £18 million.
Basildon Council officials estimate that council costs could rise to £8 million and police costs to nearly £10 million for the operation.
The council said: "The estimated direct operational cost of £6.5 million, together with estimated post-operational costs of £1.5 million, produce a total of £8 million. However, this is considered to be a worst-case scenario."