Tehran, uncharacteristically quiet today with its streets virtually deserted, awaited the start Sunday of a two-day religious holiday that Iran's opposition hopes will launch the final round of its nearly year-long effort to overthrow the shah.

Violence continued in other Iranian cities. United Press International reported that 29 persons were killed when army troops opened fire on antishah demonstrators in Tabriz and the Moslem holy city of Qom.

[In Washington, the Pentagon said that 983 dependents of U.S. servicemen and Defense Department civilians stationed in Iran had left the country by air Friday and Saturday. The Pentagon dispatched five C141 transport planes from the United States to complete this airlift, which spokesmen emphasized was not an official evacuation. About 500 to 600 dependents who have said they want to remain are still in Iran, a Pentagon spokesman said.]

Tehran looked like a city expecting a sirge. Its usually traffic-jammed streets were all but empty.

A massive exodus by road, which began in earnest Friday, today involved 130,000 cars, according to traffic officials, as residents took advantage of a long holiday weekend to escape the violence that both government and opposition decry but fear may break out.

Opposition organizers claim that 1.5 million people -- a third of Tehran -- will march Sunday in a mammoth anti-shah demonstration that will converge from seven lines to march on the Shahyad monument, which symbolizes the shah's claim to epresent continuity in the country 2,500 year history.

The march commemorates both international Human Rights Day and the annversary of Ashura, the date 1,298 years ago when Hossein, grandson of the prophet Mohammed and founder of the Shiite sect of Islam, was killed in battle.

In a further gesture toward the religious-dominated opposition, which also includes lay organizations, students and professional politicians -- the military government yesterday lifted its ban on processions.

Tonight the government announced that it was relaxing the curfew, starting it at 11 p.m. rather than 9 p.m. on Sunday, Monday and Tuesday, and it announced that army troops would not be stationed along the lines of march.

Areas covering much of north Tehran -- where the shah and many foreigners live -- are barred to the demonstrators. The list of these areas was read over the radio.

The demonstration organizers had argued that they had hundreds of marshals capable of maintaining order and that the presence of troops had contributed to bloodshed in previous demonstrations.

But the military government also warned that specially trained provocateurs and saboteurs wearing uniforms might try to make people believe they were army deserters and that others would daub themselves with red paint to feign wounds.

The army reintroduced into the capital a large number of British-built Chieftain heavy tanks and Soviet-made armored personnel carriers.

Heavy helicopter traffic was seen overhead despite the heavy fog, which gave way to driving rain.

Some 3,000 foreigners and Iranians left on regularly scheduled and special flights from Tehran Airport, which abruptly shut down at 7 p.m. until Tuesday morning.

In making the announcement of the shutdown, Iran Air, the national carrier, which flew most of its planes out of the country for safety's sake, offered no explanation for its decision. But observers noted that the protest march is due to end near Tehran airport.

Among those flying out were more than 100 U.S. embassy dependents taking advantage of Wahington's free evacuation offer for extended Christmas holidays.

In this sprawling city, residents emptied canned food shelves in groceries, which were about the only shops open.

Hundreds lined up for kerosene used of rheating and cooking and now scarce because of the six-day-old oilfield strike, which has reduced production to well below the normal 6 million barrels-a-day level. The airport ran out of JP4, the fuel used by jet aircraft.

The Intercontinental Hotel, a past target for rioters, bricked up its ground floor windows and welded steel floor windows and welded steel beams across the ballroom entrance.

Even that symbol of Western influence prudently hung black flags of mourning, which are staandard Ashura fixtures bedecking Iranian homes and offices.

Both government and oppostion made protestations of their peaceful intentions during the march, but warned beforehand that any violence would be the responsibility of the other side.

"On our side there will be calm, no provocation, no looting, no violence." said Karim Sanjabi, 75, the National Front opposition leader recently released from jail.

"If there is trouble it will start with the troops."

But government officials pointed to a leaflet they said was the work of the banned Tudeh, or Communist Party.

The leaflet asked Iranians to "transform Ashura into days of blood and fire," called for "insurrections and continued strikes to paralyze the country" and exhorted Iranians to "give our blood generously."

"Raise the blood red flag," the leaflet said, "and use flames to deny the enemy forces the means of movement and pursuit."

A high Interior Ministry offical said privately, "We fear violence from uncontrolled elements from both sides," He sighed and crossed his fingers "for tomorrow."

Police sources are especially concerned with crowd control at the Shahyad Monument at the end of the line of march, where large numbers of bunched demonstrators are to disperse following a final rally there.

An even more serious source of worry is the army. It has withstood the strains since Septmber of maintaining martial law and the repeated appeals from the shah's archenemy, Paris-based Ayatollah Ruhollah Khomeini, to throw down its arms and join the opposition.

Only two days ago three ayatollahs, or Shiite leaders, living in Qom, 90 miles south of Tehran, warned the army against using its weapons against demonstrators.

Government officials hope that by pulling troops out of direct contract with the marchers -- but not out of the city -- they can spare the army, especially draftees, the agonizing dilemma of either failing in their loyalty to the shah or shooting fellow Iranians.

One high government official stressed the "tremendous risk" the shah has taken in authorizing the processions.