Rival Iranian demonstrators, many chanting slogans and waving banners and some wielding sticks, clashed with each other and with police in a series of skirmishes yesterday on the streets of downtown Washington.

By the time the series of rallies ended in late afternoon, more than 35 persons -- including two police officers -- had been treated for injuries, mostly minor, and 169 persons had been arrested. Traffic was periodically disrupted as police chased protesters through downtown streets on foot, scooter and horse.

And to add to the mix of conflicting ideologies and police-demonstrator clashes, scores of American tourists, servicemen and other bystanders jeered the Iranians and occasionally fought with them in the streets.

What the rival factions lacked in size -- the four separate groups attracted a total of about 1,500 demonstrators -- they made up for in the intensity of their rhetoric.

The focus of the day's activities was a rally in Lafayette Square sponsored by the Iran Freedom Foundation, whose founder, exiled Iranian diplomat Ali Akbar Tabatabai, was assassinated last Tuesday in the doorway of his Bethesda home.

Police said yesterday that Daoud Salahuddin, 29, an American member of a Moslem sect who is charged as the triggerman in Tabatabai's killing, is still at large.

Among the 400 persons who attended the IFF rally were some who lamented the death early yesterday of Shah Mohammad Reza Pahlavi. But the IFF supporters, who unanimously denounced the regime of Ayatollah Ruhollah Khomeini, were outnumbered by three disparate pro-Khomeini and Marxist groups, whose 1,100 followers taunted them from Nearby streets and sidewalks, and occasionally made forays into their midst, setting off free-for-alls.

The biggest side show in the four-ring circus that clogged downtown streets and bewildered unprepared tourists occurred on the lawn of the Capitol Hilton Hotel at 16th and K streets NW.

The lawn became a refuge for several hundred pro-Khomeini Moslem students who had been routed from nearby Lafayette Square by police about 1 p.m. to make room for the anti-Khomeini rally. About 110 to 120 of the arrests made yesterday occurred near the hotel.

Two persons closely associated with the slain Tabatabai also figured in confrontations. The murdered man's twin brother, Mohammad Tabatabai, was grazed with a stick while making a speech, and a witness to the murder, Seyed Ali Mortazavi, was arrested on a charge of carrying a pistol without a license.

Mortazavi, 29, who answered the door at Tabatabai's house when a fake U.S. Postal Service letter carrier lured Tabatabai to the door by saying he had two special delivery packages for him, was arrested on Constitution Avenue after he flashed a holstered 45-caliber pistol at an Iranian passerby.

Police quickly frisked the frightened Mortazavi and confiscated his gun, as he pleaded, "I'm a target for Nahidian's people." (Bahram Nahidian, a Georgetown rug merchant, is viewed by many Iranians here as an unofficial representative of the Khomeini regime).

Mortazavi, 29, a graduate archeology student at Temple University in Philadelphia, was released from jail after posting $1,000 bond.

Mohammad Tabatabai was in the midst of a long speech, delivered alternately in English and Persian, when one or two men in the crowd in the northeast quadrant of Lafayette Square, rushed toward the microphone.

"They attacked me," said Tabatabai, rubbing the back of his neck.

Ferydoon Khoee, of Los Angeles, a member of the IFF central committee, grabbed the microphone and implored the crowd to "calm down, calm down. These are our enemies, but the police are in control. Don't panic. We want to prove we are not animals. We are intelligent."

As Khoee spoke, the attackers fled through the crowd, but one of them was wrestled to the ground near Lafayette's statue. IFF loyalists kicked and beat him until police pulled them away and placed plastic handcuffs on the attacker.

Meanwhile, Tabatabai, who wore a black suit and tie and white shirt, resumed his speech, at one point telling the sun-bathed crowd in a near whisper, "I wish my brother were here."

The IFF rally began at the Capitol, from which its members walked along Constitution Avenue and 15th Street to Lafayette Square, followed on the sidewalk by about 70 pro-Khomeini demonosrators. The rival groups taunted each other with chants, including "Death to Khomeini" by the IFF and "Long Live Khomeini" by their opponents, who included mostly members of the Moslem Students Association but also some from the leftist Iranian Students Association and the Confederation of Iranian Students, another leftist group.

When the line of march reached 15th and G Streets NW, police attempted to pinch off the pro-Khomeini forces. The pro-Khomeini students linked arms in defiance, and the police swooped in, swinging clubs and scattering the students, several of whom were whacked randomly by police. Eight or 10 students, their heads bleeding, were taken to George Washington University Hospital for treatment.

"Those cops were just waiting for us," complained Lisa Ghazansari, a 20-year-old New Yorker who is married to a pro-Khomeini Iranian. "I've heard these things, but I didn't believe it. See this, it is the blood of one of my friends," she said.

When the IFF passed the Ellipse, where police on horseback maintained 50 yards of grass between pro- and anti-Khomenini groups, dozens of Americans stood on bleachers in blue tents in the park and taunted the pro-Khomeini students with obscene gestures and calls for release of the Americans being held hostage in Iran.

Later, Americans booed and delivered catcalls as an IFF speaker, facing the White House across Pennsylvania Avenue in Lafayette Park, asked rhetorically, "what did you do, Mr. President, when your friends in Iran (under the shah) were threatened?"

Many of the Americans on the streets yesterday made no attempt to discriminate among the various Iranian groups. A similar attitude prevailed among police. Asked how he could tell the troublemakers from the peaceful demonstrators, one officer clutched his billyclub and said, "i don't try."

Meanwhile, at 16th and K Nw, 150 pro-Khomeini students, ordered out of Lafayette Square to make room for the IFF rally, joined arms, knelt and prayed while lunchgoers and hotel guestsgawked from nearby windows.

Throughout the afternoon, passers-by taunted the demonstrators, shouting "go home" and "stars and stripes forever." Several youths waved a makeshift cardboard placard that said, "Down with the Ayatoilet."

The ugliest skirmish occurred near the White House when a dozen Khomeini supporters encountered an equal number of U.S. Army enlisted men on leave from Fort Knox, Ky. A scuffle ensued over an American flag that was being carried on a pole by one of the soldiers. A Khomeini loyalist grabbed at the flag, and in the struggle, the flagpole snapped in two. l

Motorists and pedestrians alike movedout of the way as the Khomeini supporters fled north along 16th Streettoward toward their refuge at the hotel with the soldiers and police on motorscooters in hot pursuit. Outside the hotel, a stalemate developed, with police in the middle of the street separating the two groups.

Another battle of words between U.S. mlitary personnel and pro-Khomeini forces occurred on Constitution Avenue, where several marines chanted "We want war" and U.S. airman John Kozjak shouted, "I hate them. Nuke Iran.

The shah's death was applauded by some demonstrators. Mohammad Egtedari of the Confederation of Iranian Students said, "it's a blessing." The familiar "death to the Shah" chant of the leftist revolutionaries was changed yesterday to "death to Bakhtiar," a reference to former Iranian prime minister Shahpour Bakhtiar.

Mohammad Tabatabai said, "I think the death of the shah will unite different factions in Iran." He added that "since there is no government in Iran," the shah's death will not affectthe American hostages.

The Iff rally fell far short of the 5,000 to 7,000 demonstrators its sponsors had preidcted, but Khoee, attributed the poor turnout partly to the shah's death.

"We are very sad," said Khoee, but he added, "it will change absolutely nothing in Iran."

The Iff supporters who gathered in Lafayette Square were distinguished by their relatively formal dress. Manyof the Iff women wore black dresses and high heels or designer jeans and gold jewelry, and some of the men wore expensive suits. Members of the various factions took pictures of each other, as did the police.

The Iff rally broke up about 4 p.m. As the Tabatabai supporters boarded chartered buses across from the White House, safely removed from the pro-Kohmeini factions, they applauded their police protectors. D.C. police information officer Gary Hankins observed, "That's the first time in 10 years I've seen demonstrators give us a hand."