Thirty-three Iranian soldiers were treated in Western Europe yesterday for lung ailments and severe skin burns apparently caused by chemical weapons used by Iraq in last week's fierce battles on the marshlands of the Persian Gulf war's southern battlefront.

Medical specialists in West Germany told Reuter that the Iranian soldiers appeared to be victims of mustard gas, which was used widely in World War I and has been banned by the Geneva Conventions on warfare.

Iran's ambassador to Austria, Mohammed Kiriarishi, told news agencies in Vienna that the injuries were caused by rockets fired by Iraqi planes in air raids east of the Tigris River last Friday. He said there were no facilities in Iran to treat the injured, explaining why the 33 were flown by jumbo jet to Belgium, Britain, West Germany and Austria for treatment.

Witnesses at Vienna's airport who saw eight Iranian soldiers arrive told United Press International that the wounded men had blistered, discolored skin and appeared dazed.

"Some were in severe pain and were just crying out for Allah," one witness said. "They were a shocking sight."

German doctors said that none of the patients appeared to be in acute danger and that their symptons were similar to those of the Iranian soldiers treated in Europe last year, when U.N. investigators concluded that outlawed gases had been used in the war but did not directly implicate Iraq. Baghdad consistently has denied using chemical weapons.

Sharp U.S. condemnation of Iraq last year for using chemical weapons led to strains in U.S.-Iraqi relations and may have caused delays in Iraq's decision to restore formal diplomatic ties with the United States.

U.S. officials were muted yesterday in their reaction to Iran's latest charge, saying they had no evidence Iraq had used chemical weapons in the recent fighting and repeating a blanket denunciation of their use without naming Iraq.

At the United Nations yesterday, Iran's ambassador, Rajaie Khorassani complained in a letter to Secretary General Javier Perez de Cuellar that Iraq had used poison gas on Iranian troops at least five times since March 11, wounding 200 Iranians.

Repulsed in efforts last week to cut Iraq's north-south highway linking the port city of Basra to the capital Baghdad in the recent ground fighting, Iran has sought to win the advantage in the ensuing propaganda war for international sympathy and support.

Iraq has spurned Iranian offers to reinstitute a ban on the use of chemical weapons and on attacks on civilian targets unless Iran agrees to negotiations for a "comprehensive settlement" of the 4 1/2-year-old war. Iran has continued to reject a settlement unless Iraqi President Saddam Hussein is overthrown and other longstanding conditions are met.

Iraq continued to strafe Iranian cities yesterday. A military spokesman in Baghdad said Iraqi planes attacked Hamadan, Arak and the port of Bushehr. Iran confirmed the report and added that Iraqi planes had flown over Tehran during yesterday's Friday prayers but were chased away by antiaircraft fire.

Iraq reported that its warplanes had conducted a "devastating and accurate" attack on a large ship near Iran's Persian Gulf oil terminal at Kharg Island, but there was no independent confirmation of that.

Iran, overwhelmingly outmatched by Iraq in air power, retaliated against the air raids yesterday by again shelling Basra.