About 50 Iranian students and supporters picketed at the White House and the Capitol yesterday, protesting what they say in U.S. interference in the internal affairs of the new Iranian government under Ayatollah Ruhollah Khomeini.

The group also marched to The Washington Post at 1150 15th St. NW, and accused the newspaper of unfairly characterizing the Khomeini regime as a dictatorship.

"Long Live Khomeini" and "Down With U.S. Imperialism," shouted the group as it marched throughout downtown Washington at midday.

The group, organized by the Iranian Students Association in the U.S. in conjunction with current protests in Tehran against the American embassy, particularly objected to a Senate resolution condemning recent executions in Iran. "The U.S. Senate defends shah's criminials," the group shouted in reference to recently deposed Iranian Shah Mohammad Reza Pahlavi.

At The Post, a protest leader identifying herself as Simin, said The Post is "misinforming the American people about events in Iran. The government in Iran is a democratic republic, but The Washington Post describes it as a dictatorship."

Shah loyalists who have been executed, she said, were given proper trials. She acknowledged that some were tried in closed sessions, but that was for "benefit of the people . . . The people trust the revolutionary government."

Simin said the American press exaggerates the differences among revolutionary groups in Iran and plays down "positive aspects of the new government."

The new Iranian constitution now being drafted, for example, she said, will provide equal rights for women and self-determination for national minorities in Iran.