Chanting "Soviets are murderers, Soviets are liars," an orderly crowd of about 2,500, mostly Korean Americans, sang hymns and listened to emotional speakers yesterday in Lafayette Park in downtown Washington and then marched to within sight of the Soviet Embassy, protesting the Soviet Union's reported downing Wednesday of a South Korean passenger airliner.

Yesterday's demonstration apparently was the largest protest of the incident in the United States.

Near the conclusion of the 2 1/2-hour demonstration, one area Korean leader was allowed by police to walk from the corner of 16th and K streets NW, where police had contained the protesters, to the front gate of the Soviet Embassy, a block away, to deliver a letter of protest from the local Korean community.

Cho Han Young, president of the Korean Association of the Greater Washington Area, told reporters that a voice over an intercom at the Soviet Embassy told him that "they were closed today and could not accept any message."

Cho, who was accompanied in his effort by a 16-year-old Annandale girl, Michelle Sung, said the envelope contained a message from the Korean Americans in this area saying "that we are deeply grieved and angered at this shocking incident. We ask Soviet Russia to disclose the whole truth about the incident . . . and we are asking them to disclose everything that happened in this incident and to promise not to repeat this type of action on any other type of civilians."

The 4 p.m. rally, sponsored by the Federation of Korean Associations, located in Fairfax, was attended by demonstrators who came from as far away as Philadelphia. An orderly, emotional and sometimes tearful crowd of protesters wore black arm sashes and carried signs saying "We Demand a Full Explanation," "How Could You Kill Innocent People," and "Wake Up U.S. Before It's Too Late."

There were no arrests made as a result of the demonstration, both U.S. Park and D.C. police said. Police blocked traffic on 16th Street between Lafayette Park and M street and on K Street one block east and west of 16th.

Byong Hion Lew, South Korea's ambassador to the United States, said the incident was an example of "an outrageous, inhuman act on the part of the Soviets . . . Russia has to tell us the truth about committing this grave mistake she made and has to come out and apologize and at least she has to compensate the victims and the families of the innocent passengers."

Betty Wise, a D.C. resident who said she had relatives in the Soviet Union, said yesterday that she came to the demonstration "to condemn the Russians and to help emphasize the fact that they are not to be trusted.

"I'm a liberal, but the fact is, I think they can not be trusted. I just don't think you can negotiate with people like that."

Kyung Lee came by bus from Philadelphia. Holding a sign saying "You killed our friend," she said that "we are very angry with the Soviets. They're murderers, they have killed our people."

Lee said that one of the men killed when the jetliner went down, Han Tae Pac, was the husband of a friend of hers. "Our friend was killed, and now innocent children have no father. Why would they do anything like that?"