DUBAI, UNITED ARAB EMIRATES, OCT. 11 -- After a night of violence in which Iran fired its third missile into Baghdad in a week and Iraqi warplanes attacked an Iranian oil shuttle tanker, killing at least two crewmen, the U.S. Navy today escorted its largest tanker convoy into the Persian Gulf.

The reflagged Kuwaiti tankers -- Ocean City, Sea Isle City, Gas King and Gas Princess -- were sighted off Dubai this morning after making a successful passage through the Strait of Hormuz during the night.

They were accompanied by three U.S. guided-missile frigates and the USS Mount Vernon, an amphibious landing ship that is believed to be carrying supplies for two offshore bases that U.S. naval forces are setting up on large barges in the northern gulf. The bases, equipped with helicopters, commando teams and patrol boats, are designed to extend U.S. military capabilities in the waterway.

Also today, U.S. Energy Secretary John Herrington told reporters at a news conference in Abu Dhabi, United Arab Emirates, that the United States "is very satisfied with the support we are getting from the gulf countries.

"We are getting ship repairs done," he said. "We are getting refueled and resupplied. We are getting what we need."

Herrington said the Reagan administration has not decided whether to impose a full-scale oil and trade boycott against Iran, which Congress has urged.

"Any economist knows that an embargo is very difficult" to enforce, Herrington said. "On the other hand, the American people will not be in support of buying Iranian oil and {thereby} providing money to Iran that would be used to buy weapons that could be turned on American servicemen."

"Morally," Herrington continued, "that is not a tenable position for us. For that reason, I believe we must take this moral stand . . . and I would support the toughest boycott we could put together with as many countries as we can put together."

Iran's missile attack on Baghdad shook the Iraqi capital shortly after midnight. Iran's state news agency said the missile struck Baghdad's major military camp, the Rashid garrison, on the southern edge of the city.

Iraq said the missile struck a residential area, killing and wounding many civilians. Since 1985, many of the nearly three dozen Iranian long-range missiles launched against the Iraqi capital have struck residential neighborhoods close to an oil refinery, an electrical power plant, the presidential palace and the Rashid military complex.

Iran said the missile attack was in retaliation for Iraq's use of chemical weapons last week against Iranian troops encamped in the Sumar basin, an area along the central Iran-Iraq war front about 80 miles northeast of Baghdad. Iran said the gas attack killed 100 soldiers and poisoned dozens of others.

Reporters visiting the Iraqi side of the Sumar front earlier this year were shown a display of captured Iranian military equipment and found vials of atropine, nerve gas antidote, in captured Iranian medical kits.

Last winter, Iran massed hundreds of tanks and heavy artillery pieces at Sumar and launched several probing attacks, threatening to open a second front as it launched a major winter offensive near the southern port city of Basra.

If confirmed, Iraq's use of gas in the region might indicate that Iraq's military command hopes to prevent Iran from massing an invasion force on the central front this winter.

Also last night, Iraqi warplanes fired two Exocet missiles on a 239,435-ton Liberian-registered supertanker, the Rova, as it traveled empty toward Iran's Kharg Island oil-loading terminal in the northern gulf.

Shipping sources said the two missiles did catastrophic damage to the Rova, setting off secondary explosions that may have been fueled by volatile gases in the ship's storage tanks. Other reports said the heat-seeking Exocets exploded in the engine room.

The crew immediately abandoned ship, and some were picked up by Iranian rescue craft from Kharg. The Rova is one of about two dozen tankers Iran owns or charters to ferry crude oil from Kharg to makeshift terminals farther south at Sirri, Larak and Hormuz islands, which are less vulnerable to Iraqi attacks.

Iraq, however, has launched two long-range raids on these terminals in the past week, setting one storage tanker ablaze and damaging another, the Seawise Giant, the largest supertanker in the world.