Hundreds of Iranians braved freezing temperatures yesterday afternoon to attend an anti-Khomeini rally in Lafayette Park and march through downtown Washington, snarling traffic and stopping office workers on their lunch breaks.

U.S. Park Police estimated that 1,600 demonstrators participated in the march organized by the Moslem Iranian Students Society-U.S.A. to commemorate the fourth anniversary of the slaying of two leaders of the Iranian Resistance, a group opposing Ayatollah Ruhollah Khomeini's regime in Iran.

Organizer Reza Dashti estimated that 5,000 people, including Iranians from Texas, California and Oklahoma, were at the march.

"Marches like this are being held in more than 14 other countries throughout the world today," another organizer speaking in Persian told the crowd at the park. "The object of these demonstrations is to condemn the warmongers of Iran and the belligerence of the Khomeini regime."

As the Iranian demonstrators filled downtown streets with their chants, a group of 50 Filipinos and Americans demonstrated two blocks from the Embassy of the Philippines at 1617 Massachusetts Ave. NW to protest voter fraud in the Filipino presidential election and what they then thought looked like an apparent landslide victory for President Ferdinand Marcos.

Among the embassy demonstrators was Charito Planas, a veteran of Filipino politics and a former political prisoner, who was granted political asylum in this country four years ago.

At the anti-Khomeini march there were former political prisoners, too, including Narges Shayesteh, a former Iranian schoolteacher who during a news conference showed scars of cigarette burns on her skin, which she said she received when she was tortured in prison in Iran.

As the Iranians marched from Lafayette Park, up Connecticut Avenue to Dupont Circle and back to the park, they shouted, "Down with Khomeini! Hail to Rajavi!" -- a reference to Massoud Rajavi, leader of the resistance movement.

The march snaked through downtown during midafternoon, catching some office workers on lunch breaks, holding up traffic, causing some cabdrivers to curse and drawing onlookers who watched from the windows of office buildings. The colorful march included groups of people dressed in various types of clothes representing the different segments of Iranian society involved in the resistance movement, a spokesman explained.

Some men marched in dark blue jumpsuits and yellow hardhats to represent the average workers; a group of men and women wore black academic robes to represent educators, while others wore the white uniforms of doctors and nurses.

Men and women dressed in white and wearing red carnation corsages carried two large pictures of the slain resistance leaders, Moussa Khiabani and Ashraf Rajavi, who Dashti said were killed Feb. 8, 1982, by Khomeini guards. Their deaths are commemorated annually by Iranians who live outside of Iran, said Dashti.

Before the march, the demonstrators stood for two hours on the frozen ground of Lafayette Park to watch a dramatized enactment of the day the two resistance leaders were slain. As a former prisoner of Evin, a prison in Tehran, described the scene, the cast dressed in black and white striped prison uniforms acted out the scene.

In the skit the bodies of the two slain leaders were carried into the prison and guards taunted prisoners about the deaths. Some of the prisoners were dragged to view the bodies and when they did not whimper as the guards expected, they were taken out and executed.

The scene left some men, women and children in the crowd in tears. A movie screen was raised and Massoud Rajavi was shown making a speech in which he warned, "The resistance is everywhere in Iran, so be ready. The end of Khomeini's regime is coming."

The crowd, filled with emotion, responded with the most popular chant of the Iranian resistance: "Iran-Rajavi! Rajavi-Iran!"