Thousands of Iranian demonstrators brought their decades-old dispute over the regime of Shah Mohammad Reza Pahlave to Washington yesterday, turning the streets around the White House into a battle ground of scattered but bitter and bloody violence.

The clashes left 124 demonstrators and police officers injured, some seriously. Stick-wielding youths viciously attacked each other. Sirens wailed through the streets. Tear gas floated across the Ellipse and White House grounds. Trash fires burned on Pennsylvania Avenue in front of the White House.

From before dawn until long after dark, the thousands of pro and anti- shah demonstrators, here for the shah's two-day state visit, marched in serpentine lines, their colorful banners billowing under dark skies. From huge banks of loudspeakers, protesters bellowed a cacophony of political slogans in English and their native language, Farsi.

For downtown office workers on lunch break, the chanting crowds and banners gave a reminiscent taste of the mass antiwar demonstrations of the Vietnam war era.

Just as the shah arrived at 10:32 a.m. at the White House, U.S.Park Police fired tear gas to disperse demomstrators at the Ellipse as militan anti-shah Iranian students charged into a crowd of pro-shah partisans, swinging sticks and felling dozens of people.

Two-dozen mounted policemen forced hundreds of the stick-and-bottle throwing students back to the eastern periphery of the Ellipse as the tear gas floated onto the White House grounds, causing the shah and other dignitaries at the arrival ceremonies to wipe their eyes.

The pro-shah crowd - at least 1,500 Assyrian, Armenian and other Iranian-related American ethnics - reeled from the attack, scattering westward toward 17th Street NW. Children and elderly persons appeared stunned and frightened. Some of the younger men in the crowd picked up sticks and began fighting back at the students.

Police eventually scattered the crowds. For the rest of the day, the demonstrators milled about the Ellipse, Lafayette Park and adjacent streets, occasionally scuffling with police and with each other.

The shah's visit to the United States, his first since 1975, provided the back-drop for elaborate campaigns by both pro-and anti-shah factions to demonstrate their causes and neutralize each other.

The anti-shah faction - mostly Iranian students and their supporters attending American universities -are trying to portray the shah as a ruthless tyrant (see DEMONSTRATE, A22, Col.1) (DEMONSTRATE, From A1) whose repression of political rights in Iran has been supported by U.S.arms and technical assistance.

The pro-shah faction consists primarily of first-and second-generation Assyrian and Armenian ethnics from Chicago. Los Angeles and San Francisco who support the shah because of what they view as his liberal recognition of their languages and minority Christian communities in Moslem dominated Iran.

Police, Secret Service and other law enforcement agencies had anticipated possinle trounle between the two hostile factions, but the attack by Iranian students against the pro-shah crowd on the Ellipse apparently cought them off balance.

"It was such a spontaneous thing that it was impossible to keep the two sides separated," said a spokesman for the park police. "The only think they (the police) could do was use tear gas to scatter the crowd. I'm sure it prevented more injuries."

Police Protection Foulted.

Many members of the pro-shah demonstration complained of what they said was inadequate police protection.

In addition to the beatings suffered by many at the Ellipse, three vans driven by pro-shah forces, containing sound equipment and other paraphernalia, were battered by stick-swinging students.

"The park police had promised us protection if we cooled it," said Jack I.Heller, an attorney representing the pro-shah groups. "They said they would protect our six vans. Then they failed to protect the one place (the Ellipse) that we all knew would by a hot spot."

Park police had 151 officers assigned to the Ellipse, many of them on horseback, Riot-trained members of the D.C.Police Department's special operations division were on alert nearby but were not requested by park police.

The flash paint was on the northern periphery of the Ellipse where chanting Iranian students were separated only by a fall snow fence from the pro-shah crowd assembled in bleachers facing the White House.

As the cannon for the shah's 21 gun salute sounded hundreds of students began to swarm ever and around the snow fence, charging into the pro-shah crowd with sticks that had been used to hold placards.

Park police on foot and on horse back tried vainly to break up the fighting. pandemonium broke out. More police waded into the crowd and finally began to force the Iranian students eastward, away from the bleachers.

The anger of the students turned from the pro-shah demonstrators to the police. They threw bottles and sticks at the police, as well as heavy timbers seized from a construction site on the Ellipse. Some student marshals tried to stop the missile throwing but had little luck. Armed With Shields.

Many of the student were armed also with heavy plastic shields. As police routed the students to the east, some officers picked up shields discarried in the debris and used them for their own protection against the on slaught of sticks and bottles.

Early last night, the mayor's command center reported a total of 124 persons injured, 25 of them police officers.

Forty-five demonstrators had been treated at George Washington University Hospital emergency room by mid-afternoon. There persons were admitted - two for head injuries and one for a spinal column injury.

Others were treated for an assortment of lacerations and bruises, some requiring stitches. "It was incredible to see the number of doctors there,"said Pat hurley, hospital spokeswoman. "Some were there on their own, just waiting, while the rest were on duty."

For their part, leaders of the anti-shah students deny they initiated an attack on the pro-shah crowd at the Ellipse, contending that agents of SAVAK, the Iranian secret police, provoked the incident.

"SAVAK sent a group of people near our demonstrators and began shouting insults at them and then throwing sticks," said a Federation of iranian Students spokesman who identified himself only as Mobarez.

"Our friends moved forward in self-defense," he said ... "The police on horses intervened, but they attacked only the students."

Mobarez and other organizers said at least 20 students were injured, two seriouly, by police during the fracas.

Throughout the tense hours after the Ellipse incident, attorneys for the opposing factions negotited on the street with helmeted attorneys for the Interior Department, working out shifts and movements of demonstrators to keep them physically separated on the federal property surrounding the White House. More Demonstrations Today

More demonstrations are scheduled today, but because of yesterday's violence, police are imposing some restrictions.

Originally, the anti-shah faction was to be permitted on the sidewalk infront of the White House and in the Ellipse, with the pro-shah groups at a greater distance in Lafayette Park and the periphery of the Ellipse - just the reverse of yesterday's plan.

Park police said last night , however, the anti-shah demonstration permit for the sidewalk had been revoked and the entire sidewalk in frjont of the White House will be closed to all demonstrators.

"Allowing them to demonstrate on the sidewalk would present a clear and present danger," said park police spokesman George berklacy. "We were influenced by the violence this morning."

Also, police said, the pro-shah group will move from the Ellipse area to 17th and Pennsylvania Avenue NW for today's events.

Yesterday afternoon, as anti-shah students milled about in Lafayette Park, they periodically stopped persons passing through the park, asking their nationality and sometimes accusing them of being SAVAK agents.

At one point, students rushed into H Street, surrounded a car with diplomatic license plates, and began beating the car windows with sticks. The driver, a dark-skinned man who students said was a SAVAK agent, slammed down the accelerator and fled, scraping another car in the heavy traffic. Interviewed by a reporter later, the man said he was an Iranian who had been employed at the Iranian Embassy in the past. He said he was not a SAVAK agent.

Tight security was maintained throughout the day at the White House and across the street at Blair House where the shah is staying during his visit.

Sniper teams with rifles and binoculars were perched on the roof of the White House. Executive Protective Service officers with transparent plastic shields stood in a line across the front of the White House grounds. The Secret Service cordoned off the entire area around Blair House and closed Pennsylvania Avenue in front of the White House to traffic during much of the day.

The Iranian studens - who belong to four different associations split along ideological and tactical lines-accused the park police of attacking them un-necessarily and of being in league with SAVAK agents.

Spokesmen for the Moslem faction of the students pointedly disavowed the violence during the day,hers maintained that they were provoked.

A woman shouting (WORD ILLIGIBLE) loud speakers in Lafayette Park summed up the day by saying, tothe cheers of the students. "We succeeded in smashing the shah's demenstration