MANAGUA, Nicaragua, June 20, 1979

Following massive artillery bombardment of eastern Managua, National Guard ground patrols began a cautious entry today into the outskirts of the area where rebels have barricaded off several square miles.

Reporters who managed to reach other rebel-held neighborhoods, however, said the guerrillas exuded confidence that they would hold control of the eastern part of the city.

In southern Nicaragua, where a hundred-strong column of Sandinista National Liberation Front guerrillas crossed into Nicaragua from Costa Rica last weekend, reporters taken on a government tour said the area was quiet. The southern front National Guard commander said he continues to hem in the Sandinista force a few miles from the border.

Sandinistas who have occupied Leon, Nicaragua's second-largest city 54 miles north of here, overran half a dozen national guardsmen today who had resisted for the past week in the city's central garrison

The guerillas shot and killed the commanding general, Ariel Arguello. They said he tried to escape after they had taken him from the garrison.

Government rocket and artillery attacks on Leon halted, and reporters said citizens appeared cheerful in the calm streets.

The questions of popular support for the Sandinistas is expected to be an important aspect of an emergency meeting of the Organization of American States Thursday in Washington. The meeting was called by the United States, whose delegation is to be headed by Secretary of State Cyrus Vance, to discuss ways of stopping the loss of lives here.

International emergency aid organizations have estimated that hundreds, perhaps thousands of Nicaraguan civilians have been killed by government air and artillery assaults on guerrilla-occupied neighborhoods.

The Sandinista troops and their supporting militia of barrio youths say they have taken few casualties as they run from house to house, keeping a close eye on the approach of government planes and troops.

The National Guard reportedly has suffered 80 military deaths and a little more than 200 wounded since the Sandinistas two weeks ago launched what they call their final offensive against President Anastasio Somoza's government.

Those visiting Managua's slums and neighborhoods of other cities in recent weeks report little evidence of Somoza's contention that he is fighting "Sandinista communism" with the support of the majority of Nicaraguans.

"Ninety-nine percent of all Nicaraguans are with the Sandinistas," said a mother of six yesterday at a Managuan refugee center where thousands have come to escape the fighting. "We want to change the government here"

While Managuan businessmen and opposition politicians have long debated their own support for the guerrilla movement, and have feared its possible Marxist intentions, few Nicaraguans seem aware of or interested in the future political ramifications of Somoza's ouster.

Rather, many seem to view the guerrillas, of which their own children often are part, as the heroic representatives of the people.

There is widespread fear of the National Guard. "Those people have no respect for anything," said an elderly man in the refugee center. Although the fighting had apparently retreated from his own neighborhood in the western part of Managua, he said he would not go home until the National Guard cleared out.

As for the politics of the Sandinistas, while some of the leadership avows Marxist beliefs, other describe themselves as "democratic pluralists." A lengthy Sandinista program announced several months ago emphasizes that their struggle is to overthrow Somoza and establish a "peoples' government." They have said they will expropriate Somoza's extensive land holdings here, but will respect private property of those who have "participated in the struggle."

Moises Hasan Morales, one of five members of a proposed provisional government the Sandinistas named over the weekend, described himself in an interview as a socialist who does not adhere to the "Marxist model." Hasan said he expected the provisional government to take "two to four years" to stabilize the devastated country and that "early elections" would be held.

One of the principal problems in effecting a peaceful change of government here has been the absence of an opposition figurehead with strong popular support who dared to stand off from the domination of the Somozas The Sandinista National Liberation Front, itself an amalgamation of several subgroups directed by a committee, has become the symbol of popular opposition here. CAPTION: Picture 1, ABC correspondent Bill Stewart is ordered to the ground in Managua and then shot dead by a Nicaraguan National Guardsman. A Nicaraguan interpreter was killed at the same time. Photos were taken from a television screen. ABC News, via AP; Picture 2, A Nicaraguan woman in Leon mourns at her daughter's grave after the child and the woman's mother were killed in a rocket attack by a government plane. AP