In a get-tough move yesterday, a city judge slapped $10,000 bonds on most of 70 Maoist demonstrators arrested during Monday nighths pitched battle with police in Lafayette Park, and prosecutors boosted the charges from misdemeanor rioting to the felony of assaulting police officers.

U.S. Attorney Earl J. Silbert appeared before D.C. Superior Court Judge Joseph Hannon, urging the higher bonds and citing what he said was evidence that the protesters had planned the melee that protesters had planned the melee that left more than 50 officers and demonstrators injured.

Hannon agreed to the $10,000 bonds, releasing only a handful of defendants who live in the Washington area or have other local ties.

With the charges elevated from misdemeanor rioting to the more serious assault on a police officer, each demonstrator faces a possible maximum penalty of five years' imprisonment and a $5,000 fine. The rioting charge carries a maximum one-year prison sentence.

The demonstrators were part of 400 members of a Maoist group called the Revolutionary Communist Party. They came here Monday from cities all over the country to protest the state visit of Teng Hsiao-ping, vice premier of the Peoples Republic of China.

Armed with wooden sticks and poles in a scene reminiscent of militant antiwar demonstrations a decade ago, the crowd raced into Lafayette Park, hurling bottles, nails, lead weights and other objects at police. Police counterattacked, clubbing many demonstrators and arresting 70 before dispersing the rest.

In court yesterday, Silbert described what he said was the "predetermined nature" of the melee, and said police observed the demonstrators picking up bottles, bricks and rocks as they marched toward Lafayette Park. He also quoted the RCP central committee chairman, Robert Avakian, as warning the police to "expect anything."

The tough stance taken by Silbert is a departure from the traditional policy here of charging minor offenses in mass demonstration arrests. Silbert said he made the move on his own, without signals from the Justice Department or the White House, because of the ferocity of the RCP attack on police.

Defense attorneys at the arraignment hearing before Judge Hannon expressed dismay. "It's totally beyond my comprehension that every one of these people assaulted a police officer," said attorney Michael McCarthy. He said it reminded him of the 1971 May Day mass arrests in which thousands of demonstrators later received monetary compensation because their arrests were judged illegal.

Hannon granted a defense request for a hearing today for the gevernment to list in detail its charges.

Who are these young Americans so upset by Chinese revisionism and "deviation" from the thoughts of Chairman Mao Tse-tung that they would confront a phalanx of heavily armed police?

RCP leader Avakian -- who promised his followers that the public would end up saying, "Those people are crazy, but they're serious" -- is the 35-year-old son of a Democratic superior court judge in Oakland, Calif.

A high-school-football star, Avakian told a press conference last week that he had been arrested during the Free Speech movement in Berkeley in 1964, and in several other demonstrations in later years.

Yesterday, Judge Spurgeon Avakian said in a telephone interview that he could not account for his son's Maoist political activities, but he could not condemn them.

"I'm very fond of him," said Judge Avakian. "I respect him. He's his own man and has his own views... He's living the kind of life that he thinks fulfills his ideals and I'm very proud of him for that."

A demonstrator, who gave her name only as Mary, began the progression from the antiwar movement to Maoism, she said when she graduated from the University of Michigan in 1969 and discovered "college graduates were a dime-a-dozen. All I could get was a secretary's job."

She left her two children in Chicago with a friend to come here because she belived it was "important to bring out that the changes that have happened in China since Mao's death represent a turnaround to things that were happening there. They've reinstated a testing a system to get into your universities. It's reinstated an elitist society."

A Washington lawyer who has been active in left-wing groups and causes for almost 15 years said the Monday night actions were "really nothing like the 1960s. The big difference is that, first of all, the (antiwar) movement was a mass movement.

"The left, like any other group, has its lunatic fringe," said the lawyer, who asked not to be identified," "and the Revolutionary Communist Party attracts a lot of these... They have no base in the working class.They're an embarrassing group... a distraction."

But Monday's demonstraters included a 27-year-old steel mill worker from Chicago, the son of a blue-collar family who said he had been slowly converted to Maoist politics over the course of five years by a coworker.

"Every working man's getting the shaft," he said. "I've been laid off every year for the five years I've been at the mill."