The Islamic militants holding American hostages here demanded today that Iran's Foreign Ministry officials hand over U.S. Charge d'Affaires Bruce Laingen to them for questioning about documents they claim show U.S. espionage in Iran.

A Foreign Ministry spokesman said tonight that the ruling Revolutionary Council would consider the request to turn over Laingen, the top American diplomat in Tehran who has been held under protective custody in the ministry since the radical youths seized the U.S. Embassy Nov. 4.

The embassy captors also announced that they will invite Vietnamese representatives to participate in the trial of another hostage, identified as David M. Roeder, who they said flew 102 bombing missions for the U.S. Air Force during the Vietnam War.

Although the Islamic revolutionaries have consistently threatened to try the hostages as spies unless the deposed shah is returned to Iran, they have avoided pinpointing specific Americans and never before extended the scope of their planned trials to American actions outside of Iran.

Today's declarations came amid reports of renewed fighting between followers of Iran's revolutionary leader, Ayatollah Ruhollah Khomeini, and his chief rival, Ayatollah Kazem Shariatmadari, and within hours after U.N. Secretary General Kurt Waldheim quietly slipped out of Tehran.

Waldheim abruptly ended a two-day mission without seeing the hostages, their captors or Khomeini.

Although Waldheim explained through a spokesman that he urgently was needed in New York for a Security Council meeting on the Afghanistan crisis, there were signs that he merely found a convenient excuse to end a visit frustrated by threatening demonstrations and reluctant Iranian officials.

His sudden early morning departure intensified diplomatic concern that he will have little progress to report to the Security Council, which threatened to impose economic sanctions on Iran unless the U.N. envoy gained release of the hostages by Monday.

A spokesman for Waldheim said the talks were "very useful," but diplomatic sources questioned the value of just seven hours of discussions with Iranian officials, especially since Khomeini, the preeminent figure here, did not participate.

With the diplomatic impact deepening in Tehran, Khomeini once again faced a major internal uprising from Iran's Turkish-speaking minority -- the largest and best organized ethnic group in the nation, which owes its loyalty to Shariatmadari.

In the Moslem holy city of Qom today, intense street fighting erupted between Khomeini supporters and followers of Shariatmadari, resulting in dozens of injuries before militia sealed off access to the homes of both spiritual leaders, forced shops to close and blocked most entry points to the city.

Shariatmadari, the second most popular ayatollah in Iran, has openly disagreed with Khomeini about the nation's recently enacted constitution that gives supreme powers to Khomeini and little autonomy to the country's provinces.

Early last month, Khomeini followers marched on Shariatmadari's simple house in Qom, killing one of his young guards. The next day intense fighting broke out in Tabriz with Shariatmadari loyalists seizing the television station and the governor's office.

Today's fight began when Khomeini sympathizers confronted Shariatmadari's people who were walking in a large group towards the graveside of the deceased Revolutionary Guard. Once faced with the Khomeini forces, the Turkish-speaking people ripped branches from trees to use as clubs, fought off their attackers and stormed through the city smashing windows and blocking traffic.

The Turkish-speaking minority had been angered by a tape recording they received this week of a Shariatmadari statement, made in a weeping voice, that he suffered as many indignities under the present government as he did when the shah was in power.

Many flocked to Qom from Azerbaijan Province.

The city returned to calm tonight after Khomeini and Shariatmadari broadcast pleas to stop the fighting.

But when word of the Qom fighting traveled to Tabriz, the capital of Azerbaijan, Shariatmadari loyalists seized the radio and television station run by Khomeini officials and rampaged through the city destroying Khomeini posters on buildings and lampposts.

In Tehran, another outbreak of violence marred the Islamic sabbath when thousands of Islamic radicals marched from the U.S. Embassy to the Tehran Polytechnic Institute and clashed with Marxist Fedayeen guer guerrillas who were holding a rally. Severalpersons were injured in fierce fistfights that were eventually broken up by police firing automatic weapons into the air.

Almost daily for the past several weeks; armed clashed have broken out in the various provinces of Iran where ethnic and religious minorities hope to claim some form of self-rule, such as electing their own governor, after decades of repression under the shah.

The uprisings not only challenge Khomeini's ability to govern the heterogeneous country, they also distract him from the eight-week hostage crisis. The 79-year-old religious leader is believed the only one with control over the embassy captors, many of whom describe themselves as Islamic theological students.

Today, in their 87th statement since taking the hostages, the militants demanded the Foreign Ministry hand over Laingen to them at the embassy "to give necessary explanations about espionage documents found there."

"The Foreign Ministry is responsible for transferring him from the Foreign Ministry to the next of spies (U.S. embassy)," according to the statement.

On Dec. 2, the radical youths produced a purportedly secret State Department cable that they said showed that two hostages are Central Intelligence Agency agents serving under diplomatic cover.

In the alleged documents approving an assignment for the two supposed agents, Laingen is quoted as saying they "must have" cover as second and third secretaries because of the sensitivity of the then-existing situation.

At that point the captors branded Laingen as a spy who must face trial and demanded that he be released from the Foreign Ministry, where he is confined with two other embassy officials in a large reception hall.

Foreign Ministry officials, who have turned back previous requests for Laingen's return to the embassy, are believed to value his role as a liaison to Washington. Laingen's quarters at the ministry are complete with telephone and he frequently makes calls to colleagues and family members, according to diplomatic sources.