An uneasy calm prevailed in El Salvador's capital and other major cities today as guerrillas mounting a "final offensive" against the U.S.-backed government appeared to have temporarily pulled back to the countryside.

Although there was little fighting between Salvadoran antagonists today, two American photographers and a South African cameraman were wounded when their car was hit by a directional mine in a rural area about 20 miles north of the capital. They were the first journalists to become casualties of the two-day-old offensive.

Despite a mutiny by some members of the Army Saturday night in the 2nd Infantry Brigade headquarters at Santa Ana, and a communique distributed this morning by a Lt. Col. Ricardo Bruno Navarette -- who recently joined the guerrillas and called on his comrades to join the fight against the government -- the divisions among the Salvadoran armed forces appear to have been largely contained for the moment.

Government and U.S. Embassy officials are claiming that the offensive has been defeated, but reliable reports from the countryside indicate that the leftists have held some of their best trained and most heavily armed units in reserve. Despite the relative calm of today, the outcome of the struggle here is far from decided.

The Revolutionary Democratic Front, which represents the political side of the guerrilla movement, called today for a nationwide strike to begin Tuesday. The move had been debated hotly in revolutionary circles because of the failure of a previous attempt at a complete work stoppage in August. The hope among leftists now is that with the final offensive announced and under way they will be able to gain more support.

[A rebel radio station, monitored by Reuter in Managua, Nicaragua, claimed that the guerrillas had captured more than four cities, including Santa Ana, El Salvador's second largest. The broadcast also said the guerrillas have occupied several small towns near San Salvador.]

President Jose Napoleon Duarte planned today to tour Santa Ana and several other towns where fighting was heaviest Sunday in a show of control, but postponed the tour until Tuesday.

Duarte has denounced alleged Cuban and Nicaraguan intervention in El Salvador several times during the last few days, singling our propaganda broadcasts from those countries. He has also called on U.S. President-elect Ronald Reagan to "export democracy" to El Salvador and the world and to increase aid to the government here, particularly economic aid. Martial law and a curfew remain active.

U.S. officials confirmed that significant numbers of Soviet fragmentation grenades, Chinese rockets and other sophisticated weapons have been captured by government troops in the fighting, but it is not clear whether these were being supplied to the rebels directly or brought on the open international arms market. Some of their most potent armaments are U.S.-made grenade launchers and recoilless rifles.

[Late Monday night, The Associated Press reported that Venezuelan reporter Nelson Arriti was kidnaped from his downtown San Salvador hotel. Two Dutch journalists staying at the same hotel said a group of unidentified men dragged Arriti from the building shortly before dusk. There was no indication of who the men were or why they took the Venezuelan.]

The injured South African photographer, Ian Mates, 26, was working for the United Press International terlevision network. He was described as "in delicate condition but still living" by one of the doctors attending him at the Rosales Hospital in San Salvador. One of Mates' companions said he was hit between the eyes by a piece of shrapnel and that another fragment lodged in the back of his head.

John Hoagland, 33, on assignment for Newsweek, and Susan Meiselas, 32, shooting for Time magazine, were less seriously injured. Hoagland apparently has superficial head wounds, a piece of shrapnel in his right arm and a badly torn up finger on his left hand. "I'm afraid I'm going to lose it," he said coolly as he sat in the hospital.

Meiselas, who won an award for her photo coverage of the Nicaraguan war, suffered slight wounds to her head and was in a state of shock.

Meiselas comes from New York. Hoagland is from San Diego but has lived several years in Mexico City.

The three were driving along a dirt road near the town of Suchitoto at about 9 a.m., Hoagland said, when the explosion hit them. There had been no shooting in the immediate area and their car was clearly marked with signs saying "international press."

Since serious political violence among leftists, rightists and the government began here in 1979, a Mexican reporter and two Salvadoran journalists have been killed. Two members of a Dutch television crew and Kathy Barber, a reporter for ABC have been wounded. Freelance journalist John Sullivan and Washington, D.C. radio reporter Rene Tamsen have disappeared under mysterious circumstances.

Most of the foreign journalists who have disappeared or been injured were inexperienced in the brutal political environment here. All three of those wounded today, however, have spent months covering the Salvadoran fighting in which approximately 10,000 people have been killed. All three were familiar with the risks and the necessary precautions in such an environment.