Extra police are being drafted into the Windsor area today after three nights of violent clashes between white and Asian youths.
Gangs have fought battles in the streets using baseball bats and pitchforks. A Muslim-run dairy which wants to build a mosque was petrol bombed.
Dozens of officers have been deployed to stop and search youths and mounted police are being brought in.
The Queen usually spends weekends at Windsor Castle and no decision has yet been taken over whether she would change her plans. A senior source said: “We are aware of what is happening and all appropriate security measures are in place.”
Tensions have been growing between residents and the owners of the dairy, who have applied to convert an office building into a mosque for their workers.
Despite a lack of planning permission to use Technor House as a place of worship, workers and visitors have been praying there.
Violence flared for the first time on Monday outside the building in Vale Road in the Dedworth area of Windsor.
There was an altercation between a teenage boy and dairy staff during prayers. It escalated and the windows of several vehicles were smashed.
Amid claims that the boy, his mother and teenage sister were assaulted, up to 50 young people clashed on Tuesday night.
Windows of the makeshift mosque and dairy vehicles were smashed. Residents said gangs of Asian youths travelled from Slough to fight the white gang. One youth was reportedly arrested for carrying a 12-inch knife.
Dairy manager Sikander Khan, 50, said the 50 predominantly Asian workers at the dairy were now worried about their safety.
The firebomb attack took place on Wednesday night. Mr Khan said: “The youths threw a petrol bomb at us.
“The flames damaged the front of the building, but we were able to put it out with a fire extinguisher. Workers are fearful now because we are under attack.”
Nearby, one hooded youth claimed the problems had started after the previous owners, Express Dairies, left.
The 17-year-old said: “I’ve been here all my life and there were no problems with the old owners, they used to give us milk and stuff.
“We have had a couple of fights with this lot before, but now they’re taking it seriously. We want them out of Dedworth.”
Police stopped cars full of white youths and searched them as other officers photographed and videoed them. Several youths hurled racist abuse at the dairy from their cars as police looked on.
A woman living nearby, who did not want to be named, said the trouble started on Monday.
The following night numbers on both sides had swelled and there was largescale brawling.
“On Monday three young lads, about 15 or so, were in Shirley Avenue when the men came out of prayers and attacked them with pitchforks, baseball bats and iron bars,” she said. “Whether they were provoked or not I don’t know.
“I’m worried that if they allow the mosque things will get worse.”
Other residents said that late-night noise from the dairy was driving them out of their homes and they feared a mosque would make things worse.
A spokesman for Thames Valley Police said: “We are investigating incidents of disorder and criminal damage on Monday and Tuesday nights.
“These have involved groups of predominantly white and Asian teenagers. As a result of the disorder one business and at least five vehicles have been damaged.”
He added: “We will monitor the situation and are working with the community, the business and the local authority to prevent further disorder.”
A 16-year-old boy arrested on Tuesday night was charged with possessing an offensive weapon. There were two other arrests, including one for common assault, and 22 people have been searched by police. Three youths are in custody today after the petrol bomb attack.
The unrest came the day after David Cameron waded into the debate over multiculturalism, saying there could be no place for communities living “parallel lives” in Britain.
Earlier this week the Queen gave permission to convert a room at Windsor castle into a prayer room.
The room in the Saxon Tower allows Nagina Chaudhry, who works in the castle gift shops, to carry out the halfhour lunchtime prayer which is required of all Muslims during Ramadan.