NEJAPA, EL SALVADOR, NOV. 21 -- As quickly as it began on Tuesday, a nationwide offensive by El Salvador's leftist guerrillas faded today, but not before it had left hundreds of casualties, including many civilians.

It was unclear whether the relative calm today signaled a lull in the fighting or the premature end of a coordinated nationwide attack that the rebels had said would last until the end of the week.

In this suburb about 11 miles north of the capital, San Salvador, a mother carried her 9-year-old daughter Iris in her arms, pleading with passing cars for a ride to a medical clinic.

The girl, disheveled and frightened, had been struck by flying shrapnel Tuesday night, one of scores of civilian casualties in the latest offensive by the Farabundo Marti National Liberation Front (FMLN).

The government said eight civilians had been killed and 106 injured in the new fighting, which began before dawn Tuesday.

In Washington, State Department spokesman Richard Boucher, using Salvadoran armed forces casualty figures, said the fighting had left 33 government troops and 44 guerrillas dead, as well as 160 troops and 39 guerrillas wounded. Boucher condemned the FMLN for "talking about a peace settlement while raining violence and death on El Salvador's citizens."

In New York, U.N. Secretary General Javier Perez de Cuellar also criticized the rebels for launching the new attacks, saying that the action imperiled the peace talks initiated by his organization.

The question of civilian casualties could have a direct impact on U.S. military aid to El Salvador's armed forces. Congress recently voted to cut $42.5 million in military aid -- half the amount the armed forces were to receive in 1991.

But the act specifies that the aid would be restored if the FMLN launched an offensive that "threatens the survival" of the government or "engages in acts of violence against civilians."

Obviously mindful of the congressional conditions, the FMLN has insisted that the attacks, which hit army positions and other targets in at least a dozen towns in half of the country's provinces, did not constitute an all-out offensive, but rather a "limited military campaign."

President Alfredo Cristiani, equally mindful of the possible restoration of U.S. military aid, said in a televised address late Tuesday: "This cannot be called a military action, because most of those affected are civilians. It is a new terrorist offensive."

By whatever name, the attacks were more limited than the guerrillas' all-out offensive of last November, when they held positions throughout the capital for several days and turned some neighborhoods into free-fire zones.

Last fall's action was seen as an attempt to spark a nationwide insurrection and the overthrow of Cristiani's conservative government. In that respect, it failed.

However, it also provoked the violent right into human-rights abuses, including the killing of six prominent Jesuit priests -- a crime that prompted the cut in U.S. military aid and helped turn a military defeat for the rebels into a political victory.

This time, the guerrillas defined the attacks in more limited terms -- as a measure to "punish" the armed forces for human-rights abuses, such as the killing of the Jesuits, and for blocking negotiations.

However, several diplomats here said the new offensive could be a serious strategic misstep.

"Last November's offensive achieved whatever possible effect they're going to get in terms of showing force," said one envoy. "This time, it's clearly the civilian population being the most harmed. . . . I don't see how that can help them."

A woman selling refreshments here supported that assessment. "People don't want this," she said. "People don't want any more offensives."

In the slow-moving talks, the guerrillas say they are willing to demobilize and join the political process only if the 55,000-strong Salvadoran military is disbanded. The government has rejected the demand as tantamount to surrender.

The rebels say the attacks are also designed to jar concessions from the government and military. But most diplomats say that the actual effect of the new fighting will be to harden the government's negotiating position, at least in the short term.

In addition to the civilian casualties, the government stressed the damage to property and public institutions caused by the fighting. The toll included the destruction of 26 homes, two businesses, seven vehicles and two municipal buildings.

A guerrilla mortar round landed near a public hospital in the northern province of Chalatenango, but did not cause any casualties, hospital officials said.