BUENOS AIRES, JAN. 17 (SUNDAY) -- Cashiered lieuteneant colonel Aldo Rico, a leading Army dissident, who escaped from house arrest Friday, and a group of sympathizers including the chief of an Army garrison, have taken over an infantry unit in northern Argentina, the Army said early today.

Army Chief of Staff Gen. Jose Caridi said in a communique that Rico, the head of a three-day revolt in a military school last April, and "some followers" began occupying Infantry Regiment 4 in Monte Caseros, 450 miles north of this capital, at 4 p.m. yesterday.

The Army has mobilized troops from the Second Army Corps "to initiate the march to recuperate the military installations and capture the rebels," the communique said. It stressed that the rest of the Army was following Caridi "with absolute normality."

But Lt. Col. Hector Alvarez Igarzabal, head of Infantry Regiment 4 near the Uruguay-Argentina border on the Uruguay River, issued a radiogram minutes earlier, saying he had sided with Rico and would not adhere to Caridi's orders.

Rico escaped Friday morning from house arrest in a country club in suburban Buenos Aires just before Army officers arrived with an order to return him to military confinement.

Backed by about 40 supporters, he vowed he would avoid detention "until a minimum of justice is guaranteed."

Bradley Graham of The Washington Post Foreign Service reported from Buenos Aires yesterday:

The escape of Rico has highlighted unresolved tensions in the Argentine military that continue to unsettle the nation's four-year-old civilian government.

Recent moves by President Raul Alfonsin to boost military salaries and reduce the number of officers on trial for the bloody "dirty war" against leftist opponents of a decade ago have not been enough to satisfy some of the disgruntled middle-ranking men who pose the most serious threat to stability in the ranks. At the same time, government officials and senior military commanders seem determined to avoid any further appearance of an erosion of authority.

The standoff is between Rico, a decorated veteran of the 1982 Falklands War, and Caridi, the Army chief-of-staff who wants Rico caught and retired from the service. The bad blood between these two strong-willed soldiers could erupt into more trouble, Argentine commentators warned.

A military judge had placed Rico under house arrest on Dec. 30, freeing him from detention at the Campo de Mayo base where he had been held since directing an uprising there last April. With a group of supporters, Rico moved to a country club residence in the town of Bella Vista near here. He vanished early Friday just as authorities were about to order him back to military confinement.

Argentines have reacted more calmly to Rico's disobedience this time than they did last Easter when he led an officers' revolt demanding an end to trials for abuses during the "dirty war" against leftist opponents of the military government in the 1970s. There have been no massive street rallies in support of democracy, nor, as also happened in April, have any Army units rebelled in solidarity with Rico.

One reason may be that the government has sought to portray Rico's current challenge largely as a personal matter, not an institutional crisis. Officials have played down the confrontation rather than try to whip up active public support for the administration's side, as they did last Easter.

At that time, the 45-year-old commando struck a common chord among the Army's middle-ranking officers by demanding vindication of the dirty war and a purge of an unpopular high command. In contrast, his recent complaints have tended to focus on delays in the legal proceedings against him, on sanctions against his allies in the officer corps and on what Rico called an attempt by Caridi to "coerce" him into leaving the Army.

Nonetheless, Rico's case remains an important test for Caridi and the Alfonsin government. The longer the runaway officer remains at large, the weaker the government looks, several commentators said today. Alfonsin's own authority is already less than what it was last April, eroded by concessions to the armed forces and by the return of high inflation. The president's centrist Radical Civic Union party lost badly to the Peronists in nationwide elections last November.

Fortunately for the government, Rico's precipitous flight has strengthened its hand by worsening the former colonel's legal situation. Just what spurred Rico to flee, though, remains in doubt.

His wife, Noemi, says her husband was not fleeing from military justice but went into hiding for his own safety after being "slightly injured" in a brief shootout at the country club. The government says no order to fire was issued to Army units that were mobilized to enforce Rico's transfer. But authorities have confirmed that shots were fired in the room where Rico was staying.