THE IRANIAN government is now struggling to preserve itself and its power by a ruthless resort to its firing squads. But the counter-campaign of assassination of government officials continues at a staggering rate. Yesterday a plane crash killed several of the military commanders and, perhaps more significantly, the head of the Revolutionary Guard, the clerical government's chief instrument of civil control. The early reports from Tehran deny any evidence of sabotage, but you are not required to accept that as necessarily the last word. Like the earlier bombings, these deaths are very likely to be followed by another wave of executions of the government's enemies, real or suspected.

Iran's government is trying to carry out a purge of increasing magnitude, and its opposition is clearly fighting back with extraordinary ferocity. The course of these events is difficult to follow in any detail; all international news organizations but one, the Agence France-Presse, have been ejected from the country. But the scale of the violence is evident even from the fragmentary reports available here. There has been open street fighting in many parts of the country, with a notably savage outburst in Tehran last weekend. Inevitably, the Kurds have seized the opportunity to reopen their perennial rebellion in the northwest.

The immediate danger is, as always, an even more pervasive civil war leading to the collapse of all central authority in Iran. The struggle between the clerical right and the revolutionary left is already interwoven with the much older, and historically intractable, conflicts of religious sect and ethnic loyalty. Demographically, the country is a central core of ethnic Persians--about half the population-- surrounded by a rich variety of peoples with other languages, other customs and, very often, other national allegiances. It was held together for a time by the shah's military power. But the present role of the army is particularly difficult to assess. It responded more competently to the Iraqi invasion than seemed possible a year ago, and in the past few days has even won back some territory. But the army's political intentions, if any, and even its capability to exert power within the country, are only question marks.

When the Iraqi invasion began, a great wave of panic swept over the Persian Gulf region. The governments there vary only in degrees of fragility. The combination of great wealth and weak defense forces is not conducive to serenity even in the most peaceful of times. The level of anxiety temporarily subsided as the invasion seemed to settle into a stalemate. But Tehran's daily announcements of mass executions now seem to indicate that over the past two weeks the violence within the country has entered an entirely new stage. It reminds Iran's uneasy neighbors that if the worst happens and civil war becomes general, it can become contagious.