Soviets feel the heat from their Mideast involvement. Soviet ability to free hostages seen as limited

Despite the confusion over who kidnapped four Soviet officials in Beirut Monday, there is little doubt that they are Islamic militants moved by the plight of embattled comrades. An anonymous caller identifying himself as an Islamic Jihad spokesman claimed responsibility for the kidnappings of three Soviet diplomats and the embassy doctor. It said Tuesday it had executed the doctor and a diplomat.

The caller demanded that Moscow press its ally, Syria, to stop the assault by Syrian-backed Lebanese militias on Sunni Muslim fundamentalists in the Lebanese city of Tripoli. The city is largely controlled by the Sunni Tawheed Islami (``Islamic Unification'') movement.

A caller speaking for another group, the hitherto-unknown Islamic Liberation Organization, also claimed responsibility for the kidnappings. It released photos said to be of the four hostages and warned it will kill them unless the Syrian-backed assault stops. Local radio stations later said they were contacted by the Islamic Jihad saying the two groups are coordinating their actions.

The kidnapping of the Soviets -- the first such abduction of Russians in Beirut -- came a few days after Sheikh Saeed Shaaban, the Tawheed's leader, appealed to fellow Muslims throughout Lebanon to strike at the Syrians and others he said are involved in the ``massacre of Muslims'' in Tripoli.

By targeting Soviet officials, the kidnappers may have hoped to ease the pressure on the Tripoli Muslims. One of the main factions involved in the assault is the Moscow-oriented Lebanese Communist Party, which was ousted from the city by the Tawheed in 1983.

Although Syrian troops ringing Tripoli have largely abstained from involvement in ground combat so far, they are widely reported to have joined in the massive bombardment of the city and are allowing the attacking militias to operate freely in Syrian-controlled areas. There is no doubt that the Syrians could stop the onslaught if they wanted to. The kidnappers clearly hoped that pressures from Moscow would persuade Damascus to do just that.

Even if such pressures were to be forthcoming from Moscow, which is thought to be unlikely, Syrian President Hafez Assad has a track record of ignoring Soviet wishes if he believes Syria's vital interests are at stake, as he did when he first sent troops into Lebanon in 1976.

Damascus may attach high importance to subduing the fundamentalists in Tripoli for fear that radical Muslims, supporters of Palestinian leader Yasser Arafat, and other forces hostile to Syrian influence in Lebanon may take heart in Beirut and elsewhere if the Tawheed retains its grip on Tripoli.

The Syrians may instead try to persuade their Iranian allies to use their influence with the radical Islamic groups in order to secure the release of the Soviet hostages, as happened in the case of the hijacked American TWA passengers in June, analysts say.

But it remains to be seen whether Syria's strategic alliance with Tehran will outweigh Iran's moral and ideological commitment to the besieged Islamic revolutionaries in Tripoli.

The Islamic Jihad says it is holding 11 Westerners, including six Americans, who have been abducted in Beirut over the past 18 months.

Fierce battles continued to rage in Tripoli Tuesday for the fourth straight day, with the Syrian-backed militias apparently inching forward against fierce resistance from the Tawheed fighters.

More than 400 people are reported to have been killed and more than 1,000 others wounded since the fighting began in Tripoli Sept. 15. Shelling from the Syrian-controlled hills overlooking the city has caused massive damage and disruption.

Thousands of civilians trapped in the city have spent days huddled in basements and shelters without water, electricity, or food.

As many as 500,000 of the city's 700,000 residents are estimated to have fled, camping out in unfinished buildings, orchards, and even abandoned railroad cars in the surrounding countryside.

Like the majority of Tripoli's inhabitants, the Tawheed and its leader, Sheikh Shaaban, are Sunni Muslims. But Shaaban, a staunch advocate of Islamic revolution and the establishment of an Islamic state in Lebanon, also enjoys good relations with Shiite fundamentalists, who are believed to predominate in the Islamic Jihad.

Shaaban also has strong ties with the Shiite Islamic regime in Tehran, where he was accorded red-carpet treatment when he attended celebrations for the anniversary of the Islamic revolution in February last year. An Iranian delegation traveled to Damascus and Tripoli to try to mediate in the fighting, but returned empty-handed.