Nearly 70 demonstrators protesting U.S. involvement in El Salvador were arrested yesterday after one group knelt in prayer on the front lawn of the White House and another blocked traffic on nearby Pennsylvania Avenue.

The arrest, witnesed by scores of camera-laden tourists here for Independence Day festivities, culminated a month of daily demonstrations organized by the Community for Creative Non-Violence, a local radical Christian group. The demonstrators were protesting both U.S. policy in El Salvador and what organizers said is a national military budget fattened at the expense of social services.

A total of 196 people were arrested on the White House grounds during the demonstrations, which began June 2. An additional 38 protesters arrested for blocking traffic on Pennsylvania Avenue yesterday brought the total for the month-long period to 234.

Yesterday's arrests began about noon when 31 demonstrators, who had toured the White House along with ordinary sighteers, broke from the tour line and marched onto the executive mansion lawn. There, they knelt in a circle, began reading in unison a statement protesting U.S. military aid to El Salvador and held up photographs of dead and bloodied bodies of men, women and children allegedly killed by Salvadoran government security forces.

"The people of El Salvador have asked us to be here today," one of the protesters yelled. The leader of the uniformed Secret Service officers, who had surrounded the group called out, "Take them out."

The officers then took several demonstrators by the arms. Some of the protesters, including a priest and nun, walked away quietly escorted by the officers, but others, including one elderly white-haired man, decided to let the officers drag them from the lawn. All were charged with failure to leave the grounds.

A few minutes later, another group of about 38, including CCNV activist Mitch Snyder and well-known antiwar protester Philip F. Berrigan, sat down in a circle on Pennsylvania Avenue in front of the White House, joined hands and chanted until D.C. police officers arrested them. They were charged with disorderly conduct.

Scores of television cameramen and newspaper and radio reporters, alerted to the well-planned protest by the CCNV and looking for news on a slow day before a major holiday, recorded the 45-minute episode that took on the appearance of a major media event.

A crowd of about 200 watching from the sidewalks included supporters of the demonstrators, who applauded each arrest, and tourists, who ogled a photo display of alleged El Salvadoran atrocities and snapped pictures of their own of the demonstrators, police and the White House.

Marty Pepper, 27, visiting from New Orleans, learned he was in the midst of a political demonstration when he started his White House tour and was told by officials he was among a group that was going to be arrested.

"This is the right way for people to believe in what they are doing," he said, watching the arrests from the sidewalk.

His friend, Pam Cafritz of Bethesda, said she was "sympathetic toward the U.s. getting out of El Salvador."

But two 4-H members, who are in town from Illinois for a week-long class in government and citizenship and who stumbled into the demonstration, disagreed completely.

"I think it's kinda stupid because the government knows what it is doing and the demonstrators have nothing to say about it," said Jim Goss, 17, of Knoxville.

His friend, Glenn Knott, also 17, of Ellisville, agreed. "I guess they have a right to complain, but the government is in the right." Both said they had taken pictures of the demonstrators with the White House as a backdrop.