President Anastasio Somoza, his face drawn and fatigued, said yesterday that he will not bend to the demands of opposition forces calling for his resignation.

"To resign would be to open this country to chaos and anarchy" and the possibility of civil war, he said.

As Somoza addressed his news conference however, reports poured into the capital of increased violence in the countryside between the pro-Somoza military and opposition forces.

A few steps from the auditorium inside a military garrison where the conference was held, soldiers built a wall of cement blocks in front of the president's office.

Somoza, 53, spoke after a week of intense tension that began when guerrillas took over the National Palace and held more than a thousand hostages for 48 hours. On Monday, he had met at length with government and military leaders.

In an apparent result of those sessions, the president of the central bank said yesterday that businesses closed as part of an anti-Somoza general strike, begun Friday, are acting "without consideration of consequences."

The bank president apparently intending to frighten opposition businessmen who seek to pressure Somoza economically, said continuation of the strike would mean that all loans extended to closed businesses would be called for immediate payment.

At the same time, the government announced suspension of legal recognition of the Nicaraguan Chamber of Commerce a federation of merchant groups from throughout the country. Its members voted Sunday to support the general strike and close their doors.

Although Somoza appeared weary yesterday, his voice was firm and assertive:

"I intend to fulfill my constitutional duties and remain as president of the republic until my term expires" in 1981, he said. "I intend to be here to turn his office over to my duly elected successor."

Somoza said those who contend that only his resignation will bring peace are wrong. While saying that troops would be withdrawn "if the violent demonstrations cease," he acknowledged the likelihood that "more people are going to be hurt."

While noting that Nicaragua is "far from being a perfect democracy," he said the country "is far more democratic today than at any time in its history."

He called on the opposition to "take their case to the voters. Let them come up with a program and select a leader for the next national election."

He added that while the guerrillas who seized the palace last week have said that "it's the rifle that's going to make me go, I say it's the vote that's going to make me go."

The guerrillas, he said, "will not stop (their) campaign of terror if I step down. They have pledged to continue the bloodletting until they establish in this country a Marxist state or die trying."

Non-guerrilla opposition groups are sharply divided over possible outlines for a post-Somoza Nicaragua, and in their determination to include or exclude the Sandinista National Liberation Front guerrillas from a new government. But there is universal agreement among them that Somoza must go. All have refused to negotiate with him or consider any compromise that includes his continuation in office.

The move to oust Somoza has gained momentum among workers and in the countryside and many opposition leaders feel that as the crisis continues the population is rapidly becoming more radical and less willing to listen to calls for non-violence.

Direct calls for Somoza's resignation began last February following the assassination of opposition newspaper editor Pedro Juaquin Chamorro and a subsequent protest strike that paralyzed the country for three weeks.

The organized opposition groups, centered primarily in Managua, have charged the 35-year-old Somoza rule, of which the current president is the third family member to serve as president, with corruption, abuse of power and violation of human rights.

The resignation demands have coincided with an increase in attacks against the National Guard by Sandinista guerrillas.

On Monday, the government revealed an alleged plot to overthrow Somoza by a group of National Guard members who apparently felt he had responded weakly to threats against his government. While initial reports from government sources said at least 85 enlisted men and officers had been arrested, Somoza said yesterday that the number was no larger than 35.

Asked if the National Guard was divided in its loyalty to him, Somoza said, "I would say I've got 98 percent." The authorization for the use of increased force against the guerrillas by the National Guard, he said, would mean "hurting people who are completely innocent. We have to wait until they strike and try to neutralize them."

While Somoza said that a government survey Monday showed only 8 percent of Managua businesses closed, the vast majority appeared to have closed their doors yesterday in response to the strike call. Those few employes who showed at the Centro Commercial. Mangua's largest shopping center, said they had come only to pick up their paychecks. A policeman at the center reported that of approximately 100 shops and businesses located there, only 12 were open.

Soldier riding in jeeps and trucks patrolled the city under orders to arrest workers who the government said were trying to force their employers to close. There were few reports of violence, however.

Nevertheless, many areas outside the city appeared to be in a virtual state of war between youth and worker-led vigilantes and the National Guard. In Matagalta, a city of 60,000 in central Nicaragua which is considered an anti-Somoza stronghold, large barricades blocked all entrance roads.

With all stores closed, the streets empty and filled with broken glass, and many people locked inside their home. Matagalta was a battleground Monday between youths armed with revolvers, sticks and homemade bombs and the soldiers. The city appeared divided into zones held by the guard and those under control of the youth, who appeared to be acting with the support to townspeople in their area. According to the Red Cross in Matagalta, two civilians were killed Monday, and there were a number of wounded.