Egypt's young Islamic zealots, with the shah of Iran as a new target and a dead worker as their first "martyr," are becoming increasingly bold in opposition to President Anwar Sadat and his pro-Western policies.

The organized movement of Moslem fundamentalism are riding a wave of Islamic fervor sweeping Egypt and the Middle East from the example of Iran. Although so far they have only a limited following here, the extremists pose a challenge to Sadat's goverment because of their potential for arousing mob power in the teeming streets of Cairo or on the nation's 17 university campuses.

The move into the open also coincides with a rebirth of suspicion and bitterness between Egypt's 36 million Moslems and its 6 million Coptic Christians despite Sadat's careful efforts to preserve a heritage of communal harmony. Many Copts are saying the problem has arisen precisely because of the increasing appeal of Moslem extremism.

About 5,000 Islamic students took over the university here Thursday for a round of speeches, marching and chanting that included anti-Christian and anti-Israeli epithets, anti-Sadat slogans and repeated calls for expulsion of the ailing shah, Mohammad Reza Pahlavi.

"Oh Pharaoh of this age, we don't want the shah in Egypt," the students cried, addressing Sadat as an ancient Egyptian despot in a chant that in Arabic rang out in appealing rhyme. "The blood of Moslem youth will not be an offering for Sadat and the shah."

In a similar demonstration last Friday, police fired tear gas canisters after the students tried to march from Nasser Mosque in downtown Assiut back to their student housing. A worker who the students say joined their protest, Antar Kamel, as shot and killed by the antiriot squad that broke up the march, the students say.

Interior Minister Nabawl Ismail told parliment several days later that the worker already had been in the hospital and died of prior injuries unconnected to the protest. Whatever the truth, Assiut University's Islamic zealots have made him their martyr and the campus talk says a police commander shot him in the chest point-blank.

The students gathered here again Thursday, in part to shout their unhappiness over Kamel's death. Their orators, protected by crowd-control guards wearing powder-blue jogging suits with "Islamic League" lettered on the back, attacked Sadat for his welcome to the shah, his peace with Israel and the "oppression" of his Interior Ministry.

Chants of "Allahu akbar," or "God is great," rang out between speeches to build fervor among the crowd sitting under a hot noontime sun. One speechmaker led chants of, "Islam, Islam, no to Judaism and Christianity."

Apparently eager to avoid a repeat of last week's violence, riot control troops remained in trucks parked discreetly on side streets in downtown Assiut. The students, apparently as part of a deal with authorities, had free run of the campus but did not leave it for the city streets, where life proceeded uninterrupted.

A similar rally at Cairo University 10 days ago decried the shah's presence and another at Cairo's Al Azhar University in February opposed the peace treaty and the arrival of an Israeli ambassador. The protest leaders here Thursday, however, had for the first time a "martyr" to excite the crowd with and, perhaps for that reason, openly presented their previously unknown overall leader.

He identified himself as Helmi Gazar, 25, a medical student in his final year at Cairo University who accused Sadat of leading Egypt "far from God." Gazar, who comes from a village called Sers Al Liaan in the same region as Sadat's home of Mit Abul-Koom, called himself, "prince of princes" of all Islamic Groupings on the country's main campuses.

Bearded in the manner of Islamic purists -- but dressed in Western clothes -- Gazar spoke calmly and prudently in a conversation with reporters, urging that Egypt be led into more devout practice of its Moslem heritage.

"The principal thing [wrong with Sadat] is that he does not make the Koran be applied in the country of Egypt and we of course deny, or refuse, this system of life," he said. "He is away from God. We reject it all."

Accepting the shah was wrong, he said, because "he who has killed must be killed." Peace with Israel is against Islam, he added, because "anyone who takes away a piece of Islamic land is considered an enemy." And finally, Sadat's efforts to link Egypt more closely to the West are wrong because the Egyptian people oppose them.

Although some of his followers called Iran's Ayatollah Ruhollah Khomeini "our leader," Gazar expressed only a mild interest in the ayatollah's writings. Instead, he said he seeks inspiration from the books of a purist Pakistani Islamic scholar, Abul Mawdudi.

Diplomats and other observers with long experience here have said that the Moslem groups' real power lies in their potential to mobilize crowds already dissatisfied with such problems as inflation and lack of adequate employment for university graduates. As an example, they cite the role of the Islamic clergy in inciting and directing the Iranian people's political anger at the shah.

Egypt's clergy is supported by the government and little inclined to participate in the student fundamentalists' drive against the government. At least one fundamentalist preacher, Sheik Kishk, draws large crowds every Friday, however, with emotional appeals for a return to purist Islamic principles.

The growing popularity of his theme has aroused concern among the country's Coptic girls in Alexandria for marriage to Moslem youth generated an unusual protest this week by Pope Shenouda, the church leader.

To dramatize Coptic fears, the pope retreated to a monastery in the desert at Wadi Natroun, about 5 miles northwest of Cairo. He and his bishops will boycott Easter services, the church announced, to underline their contention that the government has done too little to protect Copts from Moslem abuses.

In general, Moslem-Christian relations are smooth in Egypt. Sadat and the later Gamal Abdel Nasser before him have made a point of honor of protecting the minority. Since the conversion incident, an earlier chruch-burning and two bombings in Coptic churches, however, there is increasing talk of ill will between the communities.

Reflecting this attitude, one educated Coptic woman recently said Copts should form their own militia "like the Maronites in Lebanon." A recently married Moslem said some fundamentalist friends urged him to foreswear birth control because it was "a plot" by the Copts to lower the Moslem birthrate and thereby gain more power.