Nasser Jabarouti, who at 29 years old commands the Revolutionary Guard for all the oil-rich southwestern province of Khuzestan minces no words when he talks about "finishing saboteurs and counterrevolutionaries" in this dusty, steaming-hot port city.

Surrounded by unsmiling and heavily armed militiamen, most of them unshaven youths in their twenties and dressed in jungle fatigues Jaborouti sat in a reguisitioned schoolhouse today and said:

"We are the Pasdaran (Revolutionary Gary)We are from Imam Khomeini, and if there is danger, we will finish it. For Islam, this is very important. I think there will be no trouble now in the Khorramshahr.

Indeed there has been no trouble for a week now, following months of sporadic clashes between Iranian Arabs seeking autonomy and the armed forces loyal to Ayatollah Ruhollah Khomeini, the 79-year-old leader of the Iranian revolution.

An eerie quietness has settle over Khorramshahr, located at the junction of the Karun River and the Shatt al-Arab, which empties into the Persian Gulf. Even for the Moslem Sabbath, the streets are unusually deserted. A few women draped in black fulllength veils move slowly along the sidewalk in the 115-degree heat, and here and there idle men sleeping under the stingy shade of date palms.

The same subdued atmosphere blankets Abadan, a sprawling oil city just to the southwest which has the biggest refinery in the world

For the 2 million Iranian Arabs of Khuzestan -- who still dominate the province's population despite a recent influx of Persians from the north -- the lid is unmistakably on.

We are all afraid. That is the only reason it is quiet here," said a Khorramshahr Arab, who works in the port.

A Persian employe of the National Iranian Oil Co. also alluded to the fear, saying, "It's been quite, but I think there is a fire under the ashes. I can tell by the way the Arabs look at us."

Tension under the surface is nothing new to the province, which locals still call "arabestan" and whose tribal structure was crushed by Reza Sha, father of ousted Shah Mohammad Reza Pahlavi.

That tension erupted in late May, when on "Black Wednesday" an estimated 100 persons were killed in fighting between Arabs and Islamic fighting between Arabs and Islamic guardsmen stormed two buildngs occupied by protesting Arabs, and Arab gunmen retaliated by attacking government buildings, burning cars and setting up street barricades.

After a hiatus broken by a string of oil pipeline bombings and incidents of terrorism, including a grenade blast at a mosque in which seven persons reportedly were killed and 155 injured pitched battles erupted again last Sunday when gunmen opened fire on Revolutionary Guards from the roof of the home of Arab leader Ayatollah Taher Shobeir Khaqani.

Following the gun battle, Khomeini guardsmen stormed the house and, according to Jabarouti found automatic rifles, hand grenades, handheld rocket launchers and other weapons.

What happened next is a source of much of the tension that is sweeping Khuzestan and providing the Islamic Republic's government with the most serious ethnic challenge yet, surpassing in intensity clashes between government forces and Kurds and Turkomans in the north.

Members of Khaqani's family say the ayatollah was arrested by Revolutinary Guards, a charge that has inflamed Arabs throughout the province. They say he is being held prisoner to dampen the insurrections and to prevent Khaqani from calling a strike of the Arab oil workers, who comprise at least 20 percent of the oil work force.

But Jabarouti, who is an engineer from Tehran, said he went into the Khaqai house and warned of danger from a mob. He said the ayatollah replied, "I will go to Qom. I would like to live in Qom." Although there have been reports that Khaqin is in the holy city, he has not surfaced there yet.

Compounding the uncertainty and

Compounding the uncertainty and been the arrests of an estimated 200 Arabs -- Jabarouti said 70 have been jailed in the past week alone -- and the summary execution of three men who were caught immediately after the mosque bombing and shot by a Pasdaran firing squad.

Jabarouti justified the harsh measures, saying, "this is a very important port. We must be very careful with the refineries so that there is no danger to the pipelines."

The provincial governor general, Rear Adm. Ahmad Madani, estimated that 400 to 500 "professional agitators," including communists, are active in the province. He has said that more executions will follow to stem sabotage

As two Western newsmen left the local Pasdaran headquarters a small crowd of Arabs gathered outside the heavy iron gate. One of them followed the visitors to their car and, warily eyeing an approaching Revolutionary Guard, quickly asked, "What did they tell you? Did you get lies? What they are doing here is killing Arabs and putting them in jail."

Then, as the uniformed guardsman inched closer, obviously intent on disrupting the meeting, the Arab began talking loudly about his children and his job, and the conversation ended abruptly. CAPTION: Map, no caption, By Dave Cook - The Washington Post