Col. Alberto Natusch Busch, who seized power last week from Bolivia's democratically elected government, refused today to step down despite mounting violence that included Army troops firing indiscriminately into downtown crowds.

At least four persons were killed this morning and more than 50 wounded as armored cars fired on bystanders trying to get to work and on opponents of the government, who were attempting to build barricades to block traffic on the city's main street, the Prado.

For the first time, armed snipers fired at troops in the center of the city. All telephone communications to foreign countries were cut.

Jets flew over the city again today but did not fire on demonstrators as they did yesterday. Nonetheless, today's violence was the worst since Thursday when Col. Natusch over threw Walter Guevara Azre, Bolivia's first domocratically elected president in more than a decade.

In a speech broadcast by government-controlled radio and television, the Army colonel said he would not surrender power to congress. "With sincerity and firmness we will not permit the nation to become enslaved by predator terrorism," he said.

Prior to that, they coup leader reversed a decision to dissolve congress.

Members of congress began gathering at noon today, confident that Natusch would step down. Senate President Leonidas Sanchez had conferred with the right-wing colonel earlier and told other legislators, "The political military crisis we are experiencing will be solved in a matter of hours."

By mid-afternoon, the congress had failed to gather a quorum, and congressmen said a group of about 20 would act in the future for the body A quorum of 73 is needed for the 144-member congress.

Civilian resistance to the new government, including a five-day general strike, has been growing instead of diminishing. The government clearly hoped to cut resistance yesterday when it ordered workers back to their jobs and told them they would be paid for strike days last week.

Yesterday, opponents of the Natusch government reportedly threw dynamite and Molotov cocktails at military patrols, putting at least one tank out of commission. The precise number of dead and wounded was unknown, but an orderly at Red Cross headquarters said he had counted 23 bodies at the city morgue this morning.

In poor areas on the outskirts of La Paz, streets were blocked with stones and eyewitnesses saw soliders firing at houses.

A Roman Catholic priest said he saw a woman candy vendor cut down by bullets from an automatic rifle fired by a solider 20 feet away.

Other reports from the working class neighborhoods of La Paz said Army armored units met heavy resistance from strikers belonging to the million-member Bolivian labor confederation, the nations's most important workers' organization that has lead a five-day general strike against the coup.

Dynamite explosions sporadically reverberated against office buildings, and intermingled with the wail of sirens from Red Cross ambulances.

The fighting in La Paz also overflowed to the middle class neighborhood of Miraflores, where strikers attacked the residence of La Paz's new mayor, Gen. Mario Candia Navarro, and sacked a local police precinct.

In downtown La Paz, demonstrators tore up paving stones and built barricades but were dispersed by Army troops firing long bursts from machine guns. The Army guns were occasionally answered by snipers.

Army armored units pulled back from the main downtown streets and concentrated at the hilltop governmental Murillo Square after breaking up downtown barricades.

Police who on Saturday night announced they did not support Natusch's coup took no action against the demonstrators today and were hailed with shouts of "viva" when they retired to their stations.

In washington the State Department called the situation in Bolivia 'tense and volatile," and said it feared the possibility of major bloodshed.

In a snub of Bolivia's new military leadership, the State Department also indicated today it is not interested in maintaining a normal diplomatic relationship with that government for the time being.

Department spokesman Hodding Carter said the five-day old regime has sent a note to the U.S. authorities expressing its wish to continue normal diplomatic relations. Carter said the United States has not answered the note.

In La Paz, about three dozen union and political leaders have been arrested and most have not been freed. The leaders of the military opposition are also under house arrest.

Although Natusch had said his government would be of the "revolutionary left," he is known to be strongly anti-communist. His government has issued communiques for two days warning of a communist conspiracy against him.

The ousted president Guevara has not been heard from since Saturday. Until then he and his Cabinet issued communiques through La Paz radio stations claiming they still were the Bolivian government.

Natusch has placed the country under martial law, imposed a state of seige, and ordered local press censorship. This afternoon, he ordered tele-communications companies here not to send any more cables filed by newsmen representing foreign magazines and newspapers.

At 6 p.m., soldiers with guns began to close the office of foreign wire services.