WASHINGTON (AP) _ Federal marshals seized political extremist Lyndon LaRouche's offices in Washington, D.C., on Friday, three days after taking control of his Virginia headquarters and locations in other U.S. cities.

LaRouche followers had been operating out of their Washington offices since Tuesday, when prosecutors obtained a federal bankruptcy judge's order taking control of three LaRouche-associated corporations and forcing them into involuntary bankruptcy proceedings.

U.S. marshals took control of the downtown office suite shortly after 2 p.m., changed the locks and posted ''no trespassing'' signs.

The offices were listed in the names of Fusion Energy Foundation, one of the three companies forced into bankruptcy court, and the LaRouche magazine, Executive Intelligence Review. The LaRouche organization had used the offices in the past as a location for news conferences.

In a news conference on the sidewalk outside the building, magazine contributing editor Webster Tarpley said the magazine would continue to publish.

''They're not going to muzzle the voice of a free press,'' he said.

The government took the action to recover more than $16 million in outstanding contempt-of-court fines imposed by a federal judge in Boston for failure to comply with subpoenas.

LaRouche attorney Odin Anderson said Thursday that the actions had put out of business LaRouche's national weekly newspaper, New Solidarity, as well as most other activities, although he said followers would continue conducting fund-raising activites from ''homes, pay phones, wherever.''