Moslem fundamentalists claiming to hold three Soviet Embassy officials said in a statement published today that they will not free their captives until Syria's intentions become clear.

The Islamic Liberation Organization seized three Soviet diplomats and an embassy doctor on Sept. 30 and killed one of them. On Oct. 2, the same group took responsibility, in a communique telephoned to a news agency in Beirut, for the execution of one of them. The body of Arkady Katkov, a consular secretary, was found dumped face down near the sports stadium, in Beirut's southern outskirts.

The group said its action was designed to exert pressure on the Soviet Union, Syria's main arms supplier, to help stop a Syrian-backed offensive against the northern port city of Tripoli. A Syrian-sponsored cease-fire between the Islamic Unification Movement, a Sunni Moslem fundamentalist group, and leftist parties attacking Tripoli took effect last Friday, but there is still no trace of the three missing Soviets.

"We shall continue to hold the Soviet spies until we are certain about Syria's intentions," a statement published in the daily An Nahar today said.

Strongly anti-Syrian in tone and reminiscent of tirades by the fundamentalist Moslem Brotherhood, now banned in Syria, the statement was signed by the Islamic Liberation Organization-Khalid Ben Walid Forces-Beirut Command.

Today's statement deplored Syrian actions in Lebanon since 1975, the beginning of the civil war, and Soviet military intervention in Afghanistan.

Minor discrepancies in the form of the letter, compared with previous ones that were accompanied by evidence such as photocopies of identification papers and Polaroid pictures, raised doubts about its authenticity.

Soviet Charge d'Affaires Yuri Suslikov met today with Lebanese Foreign Ministry officials and expressed his concern about the continued detention of press attache Oleg Spirine, embassy physician Nikolai Svirsky and commercial section representative Valery Mirikov. Right-wing newspapers and radio stations said a delegation of Soviet intelligence officials arrived in Beirut Monday to investigate.

The latest Islamic Liberation Organization statement, whether authentic or not, has not been denied. It made no mention of earlier communiques, which had offered to release the Soviets in exchange for a cease-fire, the withdrawal of Syrian-backed militias from Tripoli and a pledge never to attack the city again.

Syrian tanks and troops moved into Tripoli Sunday and supervised the collection of weapons from the Islamic Unification Movement, known here as Tawheed.