Three Soviet diplomats and the embassy doctor were seized at gunpoint in the Moslem-controlled sector of Beirut today in the first known kidnaping here of officials from the Soviet Union.

Shortly thereafter, a caller claiming to speak for the Islamic Jihad terrorist group told foreign news agencies the Soviets would be killed soon unless Moscow "exerts pressure against those concerned to halt the annihilation of Moslems in Tripoli with Soviet artillery guns and tanks."

This was an apparent reference to Syria, Moscow's closest ally in the region. Syria is supporting an offensive by its leftist Lebanese allies against the Islamic fundamentalist Tawheed militia in Tripoli, Lebanon's second-largest city. Fighting there during the past two weeks has killed at least 300 persons.

Today's abductions of Soviets, carried out in two separate but apparently coordinated actions, broke the pattern of previous kidnapings by Moslem militants. Westerners, especially Americans, have been the chief targets of nearly three dozen kidnapings over the past 18 months, and several Arabs and Jews also have been seized.

There was no further information here today about purported plans, announced yesterday by a caller also claiming to speak for Islamic Jihad, for a press conference with some of the six Americans being held hostage. U.S. Embassy officials said they were studying the texts of yesterday's telephoned messages, but that they had no independent indication of when or where such a press conference might take place. It would be the first public appearance of the hostages, who were kidnaped between March 1984 and last June.

The Soviets kidnaped today were identified by Lebanese authorities as Oleg Spirine, an attache; Valery Mirkov, a commercial attache; Arkady Katakov, a consular secretary, and Dr. Nikolai Sirski, the embassy physician.

Soviet officials refused to discuss the abductions with reporters, but it was learned that the embassy asked Lebanese authorities and officials of a leading Moslem militia here to assist in the search for the missing men.

"I know what you are calling about. I am not authorized to comment. Please try to reach us tomorrow. We are very busy now," a Soviet official at the embassy, who would not identify himself, said by telephone. Yuri Suslikov, charge d'affaires while Ambassador Alexander Soldatov is in Moscow on vacation, refused to talk.

Shortly after the abductions, diplomats, journalists and other official Soviets in Beirut were summoned to the embassy or ordered to remain in their homes as a security measure, sources close to the embassy said.

Sources in the Shiite Moslem Amal movement said Nabih Berri, the leader of Amal and Lebanon's justice minister, had called from Damascus, where he is visiting, and instructed the militia to spare no effort in tracing the missing Soviets. Berri was instrumental in gaining the release of Americans held hostage after the Trans World Airlines hijacking last June.

Today's kidnapings took place in early afternoon, in areas near the Soviet Embassy just off the busy Corniche Mazraa boulevard in Moslem west Beirut.

In the first, Mirkov and Spirine, traveling together, were accosted by gunmen, according to witnesses. The Soviets reportedly resisted and the attackers shot at their feet before forcing them into a car and driving away.

Security sources said three spent bullet casings were found in the Soviet car, which was recovered nearby with smashed windshields.

There were few details available about the abduction a short time later of Katakov and Sirski, who apparently were seized in an area just south of the Soviet Embassy compound.

The message from the Islamic Jihad caller named the four missing Soviets and warned that sentences against them would be carried out soon.

"The painful blow will not be in Beirut but in the heart of their red abodes splattered with the blood of innocents," the caller said, apparently referring to Syria, which concluded a cooperation and friendship treaty with Moscow in 1980 and which gets most of its arms from the Soviet Union.

"Those who have sinned deserve the fires of hell. They will not be condemned to death and their suffering will not be alleviated. This is how we harm every sinner," the caller said, quoting the Koran.

Although Soviet and Eastern Europeans here have received threats in the past, they had previously been spared in the wave of street kidnapings that has driven most westerners to Christian-controlled areas or out of Lebanon altogether.

The 1984 Soviet diplomatic book lists 45 names, but it is not known how many are here now. Soviet Embassy personnel are not allowed to bring their children to Lebanon and only few spouses are here. Soviet dependents were evacuated after the 1982 Israeli invasion.

Except for Soldatov and Suslikov, Soviet diplomats travel without body guards.

A source close to the Soviet Embassy said the embassy had received threatening letters and that he had received menacing phone calls last year saying, "We have taken French and Americans and your turn is next."

The Soviet Embassy is blocked off to traffic with cement obstacles. During the Israeli invasion and other bouts of severe fighting, Soviets often took shelter in the basement of the Soviet cultural center next to the embassy.

In Tripoli yesterday, a spokesman for the Tawheed militia appealed for support from loyal Moslems and all Islamic forces in Lebanon to put an end to the assault by "secular leftist atheist parties."

Syria has an estimated 40,000 troops in northern and central Lebanon, but it has denied direct involvement in the fighting. Syria has had a free hand in managing Lebanese affairs and orchestrating intra-Lebanese conflicts, however, ever since the multinational force left the country in February 1984.

Soviet analysts have insisted that what Syria does in Lebanon is "an internal Lebanese affair," and they say Moscow cannot tell Syria what to do. Ties between them reportedly cooled during the Syrian-backed offensive against Palestinian guerrillas in the refugee camps around Beirut in May and June.

In Lebanon, the Soviet Union has close ties with Walid Jumblatt, a Cabinet member and leader of the Druze Progressive Socialist Party militia. It has trained and armed his militiamen.

Ironically, Jumblatt's militia is the second-largest paramilitary force in west Beirut, where the four Soviets were kidnaped today.