BUENOS AIRES, JAN. 17 -- About 100 rebel soldiers led by a fugitive Army commando occupied an infantry base and small town in northern Argentina today, plunging the country into its second major military crisis in less than a year.

Reasserting demands for a "restoration of Army dignity" and an end to prosecutions of officers for the antiguerrilla "dirty war" of the 1970s, the mutineers dug trenches and set up nests of machine guns, mortars and light artillery around the town of Monte Caseros, 400 miles north of Buenos Aires.

Troops loyal to the Army's high command supported by naval and Air Force units closed in, vowing to subdue the revolt, as the civilian government of President Raul Alfonsin showed no willingness this time to negotiate with the rebels.

Attempted uprisings at two other provincial infantry units -- the 21st Mountain Regiment of Las Lajas in southwestern Neuquen Province and the 35th Mechanized Regiment in Santa Cruz Province in the extreme south -- were quashed by loyalist forces, according to military sources, who voiced concern that rebel actions could spread to other parts of the country.

Local news agencies tonight reported three additional Army garrisons in revolt in the provinces of San Luis, Tucuman and Corrientes.

Tensions have been building since Army leaders sought to transfer Aldo Rico, a lieutenant colonel who headed a four-day revolt by middle-level officers last April, from house arrest to detention at a military installation last week.

Rico, a 44-year-old commando decorated for his performance in the 1982 Falklands War against Britain, slipped away before dawn Friday from a country club near the capital, where he had been staying.

Eluding a nationwide manhunt, he arrived in Monte Caseros last night aboard a small plane and was welcomed by the commander of the 4th Infantry Regiment. An adjacent engineering unit also joined forces with the rebel leader, according to local reports.

An Argentine regiment has about 200 men, roughly equivalent to a U.S. company. As about half the men were thought to be on summer leave, it was estimated that 100 troops were in rebellion.

Phone communications between Buenos Aires and Monte Caseros were severed today, and Gen. Jose Dante Caridi, the Army chief of staff, flew over the battle-ready area to survey renegade and loyalist forces.

Many here wondered whether Argentine soldiers would actually follow orders to open fire on fellow soldiers, recalling the breakdown in the chain of command when the Alfonsin government tried to move against Rico last April. But Army commanders appeared more determined this time to enforce discipline, contending that Rico's cause had become a personal matter and his following in the ranks had diminished. Argentina was under military rule for most of the past 30 years until the election of Alfonsin four years ago.

Sen. Antonio Berhongaray, a member of the ruling Radical Civic Union and chairman of the Senate defense committee, said there is now "a readiness for combat in all the troops," in contrast with the situation last year.

Rico himself predicted shooting. Talking to reporters today, the bespectacled commando said the crisis could cause the fall of Alfonsin's government, although he added that was not his intention.

"This is not a question of arms, it is a question of will," he said when asked if his small detachment would be able to defeat government forces.

In a cable sent to all Army units, Rico said the revolt was necessary because the aims of last Easter's uprising had not been fulfilled. He listed three objectives: "a political solution for the consequences of the dirty war against subversion; an end to the campaign disparaging the armed forces; and restoration of the dignity and unity of the Argentine Army."

Rico accused Caridi of having failed to accomplish these goals and of dishonorable behavior in allegedly having fostered a split in the Army.

Rico's supporters have repeatedly claimed that their fight is an internal one against the Army's high command, not an attempt to topple the Alfonsin government. They blame "Old Guard" generals for Argentina's 1982 Falklands defeat by Britain and for failing to protect junior officers from prosecution for crimes during the military's crackdown against leftist guerrillas and dissidents in the 1970s.

The uprising last Easter, during which Rico and other middle-ranking officers seized a school at the Army's Campo de Mayo base outside Buenos Aires, precipitated the retirement of most of the service's senior generals. It also moved Congress to pass a law last June shielding several hundred officers from trial for 1970s atrocities.

But about 80 officers still face charges, and the Alfonsin government has refused to concede to demands that it fully vindicate the armed forces for wiping out leftist terrorism here. Moreover, some officers allied with Rico have been disciplined by Caridi, a 56-year-old artillery officer who assumed command of the Army immediately after the April revolt and has appeared determined to reimpose control.

Rico has been the only participant in last year's revolt to face legal charges. A dispute over whether his case should be heard in civilian or military court lasted until December, when the Supreme Court ruled in favor of military justice. That decision prompted a military judge on Dec. 30 to release Rico from detention at the Campo Mayo base, where he had been held eight months, and place him under house arrest.

But when Rico chose to spend the time at a country club residence, entertaining numerous visitors and surrounded by armed loyalists, Caridi sought to have the rebel leader transferred back to detention at a military facility.

A communique issued this afternoon by the Army's high command said the new mutiny was "in open opposition to the immense majority of the Army which responds to its natural commanders." It described the rebels as a "minuscule group" serving the "personal ambitions of its protagonists" and driven by a "messianic attitude" that is at "absolute odds with the general interests of Argentine society."

Three brigades of loyal troops and armored vehicles were reported rushing to Monte Caseros, a small town near the border with Uruguay and Brazil. Reporters there described rebels, clad in combat gear and with faces painted black, planting dynamite charges on the bridge that serves as the only access across the Timboe River to the town.

During last year's uprising, millions of Argentines poured into streets responding to government calls to show support for democracy. No large demonstrations have taken place during the current crisis, which comes at the height of the southern hemisphere's summer vacation season.