About 600 Iranian students marched in front of the Embassy of Iran, The Washington Post and the National Press Building yesterday to assert their belief that a theater fire that killed hundreds of people in Iran over the weekend was set by Iranian secret police.

Carrying signs reading "Down With The Shah," and "The Shah Burns The People,, The U.S. Press Blames The People," the protesters gathered in front of the Post of 15th & L streets NW to complain about the news paper's handling of the story.

The Post's lead article yesterday, headlined "Terrorists Kill 377 by Burning Theater in Iran," was an account by special correspondent William Branigan, who quoted government sources as saying anti-shah fanatics had started the fire.

One of the student leaders, invited inside the Post building by Managing Editor Howard Simons, said that information her group had received from sources in iran led the student protestoers to conclude that SAVAK, the shah's secret police, had set the fatal fire in order to arouse public support in the government's battle against dissidents.

The woman, who called herself "Fatima", told Post editors that all the doors to the theatre had been locked, and the incident was not publicly reported for 13 hours, with no explanation for the delay. She asked that the Post look further into the matter. Simons agreed that it would.

The students, marching in a block-long procession with four to eight people abreast, wore masks to hide their identies and, like "Fatima", would not give their real names for fear of reprisals against relatives in Iran.

At the National Press Building at 14th & F Streets NW, groups of the demonstrators went to various media offices to solicit interviews on the students' account of the fire.

"Fatima" said the students were part of the 2,500-member Iranian Students' Association, which had gathered from all parts of the country to stage a demonstration at CIA headquarters last Friday. The students had been scheduled to leave town yesterday, but decided to stay for another protest after reading news account of the fire, "Fatima" said.