Thousands of Northern Irish Catholics demonstrated peacefully here today to protest the British initiation 14 years ago of imprisonment without trial for suspected terrorists.

The anniversary often has been a day of violence. Although the British canceled this "internment" policy four years after it began in 1971, and following strong parliamentary and international protests, it is still a major Catholic rallying cry.

Among those who marched were dozens of American sympathizers of the outlawed Irish Republican Army who have spent the past week here under the auspices of the New York-based Irish Northern Aid Committee, or Noraid. The British and Irish governments, as well as a U.S. court, have charged that Noraid is the principal IRA fund-raising group in the United States.

The U.S. delegation carried an American flag during the parade, and tour leader Richard Lawlor, a lawyer from Hartford, Conn., told a cheering Catholic crowd that "we are one with you and will never desert you."

Police and British military forces anticipated the reappearance of banned American Martin Galvin, who sparked a police charge at last year's march in which a man was killed.

Galvin, a New York lawyer, is Noraid's publicity director. He denies that the group provides funds for IRA activities. Prior to last year's internment anniversary, the British government declared his presence here provocative and ordered that he not be permitted to return to the province.

But Galvin apparently slipped undetected over the Irish Republic border Friday to appear at the funeral of an IRA man in Londonderry.

Officials of Sinn Fein, the IRA's legal political arm, said today that Galvin's Friday appearance had made its point, and they did not want to risk a repeat of last year's violence by a reappearance today.

In Dublin, journalists of the state-financed Radio Telefis Eireann protested a decision of the network not to broadcast an interview with Galvin by striking for more than 24 hours, imitating colleagues at the BBC who staged a similar work stoppage last week after cancellation of a television documentary featuring an alleged IRA leader.

Sinn Fein leader Gerry Adams, also alleged to be a top IRA offical, marched today alongside the American delegation. Asked about the BBC strike and the attention it focused on his cause, Adams said the controversy was a "short-term plus," since it "exposed the lengths to which the British government is prepared to go."

Over the long term, however, Adams said, the BBC conflict probably will have a negative effect on the willingness of journalists to cover the militant republicans, who seek to drive the British from the north and unite the province in a socialist entity with the Irish Republic.

The Americans who did appear today, marching under the gaze of dozens of armed police and British Army units, were a varied collection of mostly third- and fourth-generation Irish Americans. Many said they felt morally bound to protest what they called British oppression of the Northern Irish Catholic minority. Many, but not all, said they were Noraid members.

The Noraid tours started three years ago as a way of boosting financial contributions and allowing sympathizers to "see what it is like to live as an Irishman in occupied Ireland," Lawlor said. Noraid insists that the thousands of dollars it collects each year go to humanitarian aid for families of dead or imprisoned IRA activists.

Lillian Roche, a Baltimore caterer, was on her first tour here, and marched carrying a banner that read, "England Get Out of Ireland." She said she had come on the tour to "see if the things I read about and heard are actually the things that go on." What she has found, she said, is that the "things that I've read don't tell nearly the whole story" about a Catholic community that is "totally oppressed" and suffers "harassment from the British government."

British officials, citing efforts to respond to Catholic grievances that helped set off "the Troubles" in 1969, point to local changes and expansion of opportunities for the Catholic community since then.

Like the other 125 or so members of this year's tour, Roche has spent the past week living in the homes of Catholic families and traveling around Northern Ireland. She attended the funeral where Galvin appeared, surrounded by a masked IRA military contingent under the gaze of a multitude of British troops -- who refrained from acting. Authorities said an attempt to seize him might have caused civilian casualties.

Asked about the terrorist attacks, Roche said she "couldn't morally support" bombings "if I thought that it was just killers at random. I have a family myself."

"I think that only a madman advocates violence, but there is a war here, and in a war innocent people get hurt." She added that "I don't think they're in it to kill innocent people."