Twenty-four robed Klansmen came to the Washington area yesterday and rallied without incident in a secluded Montgomery County field.

But reaction to their much heralded gathering at Lake Needwood Park, just north of Rockville, was far from small. The two dozen hooded, but not masked, members of the Invisible Empire of the Ku Klux Klan were ringed by almost 300 police officers, observed by 140 reporters and photographers and protested against by more than 1,800 demonstrators who marched, miles away, in downtown Washington and Silver Spring.

An estimated 1,500 protesters trekked from the Capitol to the Ellipse, where speakers charged that the Reagan administration has created a climate of hate and fear conducive to a resurgence of the Klan.

"Nothing is a more vicious symbol of the worst the United States has to offer than the Ku Klux Klan," Del. Walter E. Fauntroy (D-D.C.) told the gathering. "It is a symbol of hatred, violence and murder all over the world."

"Despicable scum of America, is what the KKK is," said Rep. Parren J. Mitchell (D-Md.).

Another 300 anti-Klan demonstrators rallied at Woodside Park in Silver Spring where Montgomery County Executive Charles W. Gilchrist said, "All of us are here because we hate everything the Klan stands for . . . . "

Except for one group of 100 protesters that tried unsuccessfully to confront the Klansmen at Lake Needwood Park, the counterdemonstrators were nowhere near the Klan rally and never saw them.

Hardly anyone saw them. The park was closed to the public, a tight cordon of heavily armed Montgomery County police blocking all but the 24 Klansmen and the press from the rolling grounds. Police searched Klan cars entering the park for weapons. None was found, police said.

County Police Chief Bernard Crooke said the unusual precautions were taken because of "high emotions" surrounding the Klan and intelligence reports that some anti-Klan groups planned violent counteractions.

All told, security at the park included 250 county officers, 30 Maryland-National Capital Park and Planning Commission police, six horse-mounted officers, several police dogs, plus a platoon of state troopers and a helicopter on standby.

At the Klan rally, billed as a "Support Your Police" demonstration and denounced by Montgomery County police officials, Imperial Wizard (national chief) Bill Wilkinson said the group had gathered to "honor the police" and generate support for them.

Robed demonstrators carried signs that said "Automatic Death Penalty for Cop Killers," "Police Die. Their Killers Live. Why?" and "The Next Time You Need a Cop Call A Commie Instead."

Dressed in a dark blue suit and one of the few Klansmen without a robe, Wilkinson spoke from the back of a pickup truck. He blamed a "handful of communists" at the park entrance for keeping the public out.

He said the Klan deplores recent acts of vandalism in Montgomery County, which included slurs sprayed on a synagogue. He urged people to "step forward and bring those responsible to the police."

Wilkinson criticized affirmative action programs as "nothing but discrimination" and said "desegration has destroyed our education."

The Klan, he said, is trying to "protect a way of life. I believe that God commands us to segregate the races and keep them apart. We don't hate other races . . . . We are just following God's commands."

During the rally, about 100 members and sympathizers of the Progressive Labor Party, a militant Marxist group, tried to enter the park but were blocked by police.

"We believe in going on the offensive and attacking the Klan--physically," said PLP organizer Gary Young, 30, a Metro bus driver, noting that the PLP had attacked Klansmen at a recent rally in Boston. Several counterdemonstrators carried large sticks yesterday.

Another Klan group, the Knights of the Ku Klux Klan, has asked for a permit to march down Pennsylvania Avenue Nov. 27, the first major Klan appearance in the nation's capital since 1925. About 25,000 men, women and children participated in that march.