Eighteen anti-Soviet demonstrators were arrested yesterday after they disrupted downtown traffic briefly and attempted to chain themselves to the gates of the Soviet Embassy on 16th Street NW to protest the opening of the Olympics in Moscow.

In a quickly excuted surpirse tactic, the protesters parked eight cars bumper-to-bumper in two lines across 16th Street in front of the embassy at 9:55 a.m., blocking traffic until police cleared the streets about 20 minutes later.

All 18 protesters were charged with violating a federal law prohibiting demonstrations within 500 feet of any foreign mission.

The group that identified itself as the Association of Lithuanian American Young People, said it was protesting the Soviet invasion of Afghanistan and its occupation of Lithuania since World War Ii.

Among the protesters were an aide to Sen. Richard Schweiker (R-Pa.), a a Roman Catholic priest, an engineer, several teachers and graduate students andSimas Kudirka, a former member of the Soviet merchant marine whose attempted defection to the U.S. in 1972 sparked an international incident.

Many in the group said they had relatives in Lithuania who had suffered persecution under the Russians.

The protesters placed a green, red and yellow Lithuanian flag, black drapes and a sign reading "Lithuania 1940 -- Afghanistan 1980" in front of the embassy.

They also draped a large "Free Lithuania Now" banner across 16th Street near L Street.

"The Russians have to know that the average middle-class American is mad at what the Soviets are doing to the Jews, the Ukrainians, the Lithuanians and now what they are doing in Afghanistan," said Linas Kojelis, an aide to Sen. Schweiker.

"I know the life there. These people are gangsters," Kudirka shouted, glancing at the embassy, before he was arrested. "Why don't you reporters open the eyes of America."

Kudirka, a native Lithuanian, jumped from a Soviet ship onto a Coast Guard cutter in November 1972 in an effort to defect. He was refused asylum and his subsequent trial and imprisonment in a Soviet camp was the subject of a recent television movie.

Now a U.S. citizen, Kudirka said he traveled to Washington for the protest from his home in New York where he works as a caretaker at the Lithuanian Cultural Center.

Asta Banionius, one of the protesters and a secretary, said she got permission from her employer to take the day off since she expected to be arrested in the protest. She said she was "following in my father's footsteps" because he, a native Lithuanian, had been in a 1940 student demonstration against the Soviets.

The protest began when the demonstrators approached the embassy in their cars through a nearby alley and quickly left the vehicles parked across the middle of 16th Street between L and M streets.

Some of the protesters had chains around their bodies that they tried to attach to the gates at the embassy, but were prevented from doing so by the U.S. Secret Service uniformed officers.

Soviet Embassy employees walked back and forth in the front yard of the embassy during the protest but seemed to ignore the demonstrators.

The protesters surrendered peacably, even good-naturedly, to police. "Are you one of the protesters," a police officer asked a young woman from the group.

"You bet i am, don't forget me, " the woman replied.