Three nights of battles between young people -- most of them black -- and riot police in South London have seriously damaged already deteriorating race relations in Britain.

The disorders left more than 200 people injured and the area's commercial center devasted by looting and firebombing.

In scenes reminiscent of disturbances in American black ghettoes, the violence began with a confrontation between police and bottle-throwing youths on Friday, became a full-scale riot last night and erupted again tonight. At the height of the violence last night, as many as 1,000 youths in roving gangs fought an equal number of police with bricks, iron bars and Molotov cocktails until early morning.

In what a police official described as "an orgy of looting and setting fire to premises and vehicles," scores of jewelry, appliance and other stores were looted by both blacks and whites while two dozen buildings and as many cars and police vans were burned. The Brixton area was littered today with overturned, charred vehicles, gutted buildings, bricks and broken glass.

Police said 165 officers were injured last night, 24 seriously. Twelve firefighters and at least 18 civilians also were hurt, and police armed with clubs and riot shields arrested 106 persons last night. No firearms were used on either side.

More violence tonight, with 85 more arrests and 26 police injuries, followed a day of tension as hundreds of police remained in the area. Although traffic and public transportation had been cut off, the streets again filled with both blacks and whites, until the rioting tapered off after nightfall.

When Deputy Prime Minister William Whitelaw and London Police Commissioner David McNee toured the area on foot under heavy escort this afternoon, they were taunted with shouts of "Sieg Heil." Then, while they visited injured police officers in a nearby hospital, a few hundred youths again pelted police with bricks and bottles.

It was the third major clash between blacks and the police in Britain in the last two years. As in the previous incidents, Brixton residents, community leaders and local politicians today blamed the violence on police harassment in the racially mixed neighborhood, where immigrants from the West Indies first settled in the 1950s.

Denying mistreatment, police officials blame social problems beyond their control, including racial discrimination and Britain's economic decline. Assistant Police Commissioner Wilfred Gibson said these problems included "unemployment, housing conditions and discrimination against young West Indians by employers -- all things beyond police control."

Many Brixton blacks complained, however, that they have been stopped repeatedly on the street or while driving their cars for minor violations such as not signaling turns, and that the police abuse them verbally and physically. They especially resent frequent police use of the so-called "Sus" law to stop, question and even jail "a suspicious person loitering with intent to commit an arrestable offense."

Government studies show that many more blacks than whites are arrested under this law, and an all-party parliamentary committee has recommended its abolition.

"They're antagonizing us," said a black shopkeeper in Brixton. "If I left my shop and wandered down the street, I'd be stopped eight to 10 times."

Residents claimed the police made matters worse this weekend by flooding the area with officers after the brief clash Friday night in a misunderstanding about police treatment of a black youth stabbed on the street. Police said they responded in "a fairly low-key" manner and that things got out of hand only after Brixton's streets filled with youths yesterday and someone badly injured a police officer with a thrown brick.

Gibson added that Braxton has to be policed with greater intensity because it has Britain's highest crime rate, including 50 to 60 robberies a week. Asked about community leaders' suggestions that the police should have been less visible as tension built during the weekend and withdrawn during the height of the violence, Gibson added, "We have to maintain law and order."

Both McNee and Gibson also suggested there may have been advanced planning or outside assistance for the rioting. McNee said police are investigating "unconfirmed reports" of this.

"We have no idea whether it was organized, but it seemed very coincidental that large numbers of black youths suddenly appeared on the streets," Gibson said. "Large stocks of Molotv cocktails were appearing at will."

McNee previously has suggested that "militants" had been "motivating and urging the black community to confront the police." While this underestimates black suspicions of the police, there is evidence that left-wing activists have been trying to capitalize on growing black alienation while neo-Nazi groups on the far right have been recruiting white youths for marches and attacks against blacks.

Only about 4 percent of Britain's population is nonwhite, consisting primarily of nearly 2 million West Indians, Pakistanis and other Asians and Africans. But they are concentrated in industrial inner-city areas where they were sought after World War II for heavy work disdained by native Britons.

Now they face unemployment rates two to five times higher than the rest of the population. Brixton is about two-thirds white, but young blacks account for more than half its steadily increasing number of unemployed.

Although immigration of nonwhites has been slowed to a trickle in recent years by increasingly restrictive laws and an increasing number of blacks are British by birth, they still face considerable antagonism. This is made clear by opinion polls, public statements by prominent anti-immigrant politicians, and the actions of racist extremist groups.

Only two weeks ago, in a speech reported on many newspaper front pages here, Enoch Powell pointed to the growing proportion of blacks in British cities, warned of "violence on a scale which can only be described as civil war" and urged that they be moved out of the country in "a reimmigration hardly less massive than the immigration that occurred in the first place." Powell, a former Conservative Party Cabinet minister who was fired 13 years ago for his extreme views on race, is now a member of Parliament representing an Ulster Unionist constituency.

Prime Minister Margaret Thatcher, while stating her opposition to "racism or fascism," has said she can understand how Britons in some neighborhoods could feel "swamped" by nonwhite newcomers. Her government has sent legislation to Parliament to change the country's citizenship laws and end the British tradition of automatically granting citizenship to everyone born here. Black community and civil rights leaders fear this will prevent a large number of children of nonwhite immigrants from becoming British citizens.

Meanwhile, member of neo-Nazi and British Movement have attacked blacks on the streets and terrorized their homes in some areas. They also have staged frequent, provocative marches.

Some blacks and Asians have responded by joining vigilante groups and staging counterprotests, often organized by white left-wing activists. The government recently banned neo-Nazi marches at least temporarily in London and some other cities.

Discrimination of various kinds against blacks in employment and housing has been documented by government reports.