Sons fight their fathers in Iran; Rebels challenge regime with bombs, guns

In post-revolutionary Iran, the violent regime of Ayatollah Ruhollah Khomeini is being challenged by an equally violent guerrilla movement.

Although the tactics of the internal fighting have changed over the past year , the ruthlessness has not.

''The armed struggle is the only way to get rid of that regime,'' says Massoud Rajavi, who leads from Paris the guerrilla resistance known as the Mujahideen-e Khalq.

Mr. Rajavi's group is held responsible for last year's bombing of the headquarters of the ruling Islamic Republican Party (killing at least 72 persons), as well as for the murders of one prime minister, a president, and dozens of officials of the Islamic Republic.

''Now we have changed our strategy,'' he says. ''Instead of famous figures, we kill those responsible for the daily repression.''

No exact figures are available on the number of low-level agents killed in recent weeks. But those who check the obituary pages in the newspapers put the number at about 50 per week in the country.

''We carefully select our targets,'' Rajavi says. ''I am very optimistic. In a few months we will be able to organize a general uprising.''

But the Islamic regime has so far shown an incredible ability to survive. Despite the loss of almost all of its high-ranking leaders last year, the regime can still count on hundreds of thousands of supporters who are ready to die for it.

A shopkeeper says of a recent guerrilla attack: ''Within an hour a mullah came to replace one of his colleagues who had been murdered at our neighborhood committee.''

It is difficult to assess the importance of the present support for the guerrilla movement within Iran. Before being banned, the Mujahideen-e Khalq were able to organize huge rallies. In the parliamentary elections last year, Rajavi got more than half a million votes in Tehran alone.

The typical supporter of the resistance is in his teens or 20s and has received at least some formal education.

The government apparently hopes that terrorist actions will undermine popular support for the Mujahideen-e Khalq. But so far their support doesn't seem to have eroded. Their newspapers published in Kurdish-controlled areas still circulate clandestinely in Tehran. The newspapers are clearly printed but very small so that they can be easily hidden.

Once a Mujahideen-e Khalq hideout is discovered and surrounded, the assault is carried out by Revolutionary Guards. Recently, in the north of Tehran, the guards evacuated an entire neighborhood and then brought in heavy weaponry. The guerrillas, who know they will be executed if caught, rarely surrender. They try to shoot as many Revolutionary Guards as possible before being killed themselves.

The fight is often fratricidal. Families once united in the fight against the Shah are now split. A month ago, Ayatollah Gilani, a religious judge who has sent dozens of opponents before the firing squad, learned that his own son, a member of the Mujahideen-e Khalq, had been killed. A representative to the legislative assembly has had two sons executed. And the late Ayatollah Hassan Lahouti, once a Khomeini aide, discovered the body of his son at a prison morgue.

Despite the lack of coordination between regular forces, committeemen, and Revolutionary Guards, the government has had some success in its fight against the Mujahideen. Hundreds of militants have been killed or executed. But, far from being dismantled, the organization has proven that it is still able to strike effectively.

''They are as stubborn and as courageous as the mullahs,'' says an official of the former provisional government which operated briefly after the Shah's departure.

More than a fight between leftists and rightists, the present war is a conflict about what the Islamic revolution should be. Fundamentalists and the Mujahideen are driven by the same faith. They both believe they are fighting for the truth, and no compromise seems possible.

Even compromise between Rajavi's guerrilla movement and political opposition forces within Iran appears difficult. Many of these groups condemn Rajavi's policy of assassinations. ''He is like a Maoist: He raises the red flag but in fact is a tool of imperialism,'' says Nourredin Kianouri, the secretary-general of the very pro-Soviet Communist Tudeh Party, whichbacks the ruling fundamentalists even though communists are often persecuted in Iran.