The Iranian government move armored units and troop reinforcements into this troubled city today in an attempt to crush ethnic Arab unrest after two days of violence.

The show of strength came after scores of people died in clashes between ethnic Arabs seeking autonomy and Persian followers of Ayatollah Ruhollah Khomeini. Arab spokesman said about 200 persons had been killed. The city and its environs remained extremely tense.

The government also deployed Khomeini's Revolutionary Guard units to reinforce security forces guarding the world's largest oil refinery at neighboring Abadan. Guards were posted along important pipelines to prevent potential acts of sabotage.

By nightfall, the government action appeared to have contained the fighting, which earlier threatened to spill over into other towns of Khuzestan, the oil-rich southwestern province whose Arab residents prefer to call it Arbestan. Most of Iran's 2 million ethnic Arabs live in the province.

The clashes that started here yesterday and Arab demands for political autonomy comprise the most serious outbreak of ethnic violence that has plagued the new Islamic Republic. The Arabs want to create an autonomous Arabestan with looser ties to the central government in Tehran and more local control over the province's natural resources.

Gun battles in and around this port city continued this morning despite a declaration of a "state of emergency" by the provincial governor general, Rear Adm. Ahmad Madani. By late afternoon a lull settled over the city and Arab leaders were attempting to arrange cease-fire negotiations.

Aides of Arab leader Ayatollah Taher Shobeir Khaqani complained, however, that instead of sending a negotiating team from Tehran to thrash out the problem, the government sent military commandos to reinforce troops and Revolutionary Guards in the area.

With no negotaitions yet under way, residents feared that new clashes could erupt at the slightest provocation.

"There is no authority in the town and no one to talk to," said a nervous aide of Ayatollah Khaqani. "There is nothing but anarchy all over the place."

He said the Khaqani camp had contacted the government in Tehran and the Khomeini entourage in the holy city of Qom to ask for negotiations but had received no answer.

The aide put the casualty toll in the fighting that began before dawn Thursday at 200 dead and 600 wounded. A Western diplomat stationed here disputed the official radio report of 31 deaths and estimated that more than 100 people lost their lives.

Khaqani aides said there was heavy shooting throughout the night and charged that Iranian naval torpedo boats on the Karun River fired with machine guns on Arab neighborhoods of Khorramshahr.

Iran's biggest commercial port, Khorramshahr is located at the junction of the Karun River and the Shatt al-Arab, which empties into the Persian Gulf It is the shipping hub of this oil-producing province.

Armed Arabs and Iranian troops exchanged automatic weapons fire across the Karum River near the Khorramshahr naval base. A group of Western correspondents who tried to reach base this morning was forced to turn around by gunfire from Arab positions on the river's northern bank.

Iranian soldiers in camouflaged uniforms crouched behind a retaining wall on the opposite bank. Nearby the body of a civilian killed by three rifle bullets lay in the street.

shooting also flared near an army base outside Khorramshahr. Soldiers guarding a gatehouse on an access road from a highway to the base fired bursts from a 30-caliber machine gun in the direction of mud and brick houses across the road after coming under sniper fire. CAPTION: Picture, Arab sniper at his post in Khorramshahr, site of fighting between arabs and Persians in Khuzestan. AP