Several hundred followers of Ayatollah Ruhollah Khomeini's chief religious rival in Iran tonight shouted "death" to Khomeini's representatives here and approval of the capture of nine militiamen sent by the central government

Waving axes and wooden staves over their heads in the cold night air, the demonstrators urged their religious leader, Ayatollah Kazem Shariatmadari, to avenge a militia attack Thursday night on their political party headquarters in this northwest provincial captial of East Azerbijan.

"Shariatmadari, we are your soldiers, we will die for you," chanted the crowd, which lit up the dark night with raging bonfires. It had assembled in front of the heavily fortified Moslem People's Republican Party, the political organization loyal to Shariatmadari in this Turkish-speaking area.

Any clash with the independent and populous Azerbijanis would create grave dangers for Khomeini. He also faces loyal challenges from Baluchis in the southeast, Turkomans in the northeast, Kurds in the west and Arabs in the oil-rich southwest.

The provinces of East and West Azerbaijan contain the largest minority in Iran -- one-third of the nation's population -- and battles here could spark revolts in other regions where calls for autonomy are equally strong.

Inside the office of the Moslem People's Republican Party, the building once occupied by the political party of the deposed shah, were dozens of masked and armed men, lined behind sandbags. They pledged to hold the nine militiamen until Khomeini's hand-picked officials leave the province and jailed party members are freed.

"If you let the hostages go, we will kill them ourselves," the demonstrators responded. It was a loud, angry mob similar to the crowd that took over the television station and governor's office here two weeks ago after Khomeini forces shot a Shariatmadari guard in Qom.

Across town, religious and political leaders loyal to Khomeini was trying to extinquish this latest in a series of regional uprisings challenging the rule of the nation's spiritual and revolutionary leader, Khomeini.

Although negotiations were underway to bring about a peaceful solution, Khomeini supporters were planning retaliation unless the militiamen are released. "If we don't get them back, we'll march tomorrow," warned Sayed Hassan Hosseipi, a Khomeini representatives in the talks.

After the bloody street warfare in Tabriz earlier this month that left at least seven dead, anti-government fighting broke out in Baluchistan Province, a government-owned natural gas pipeline was blown up in Arab-populated Khuzestan and fighting was reported in Kurdistan.

Moreover, Shariatmadari, the nation's second most popular religious leader, commands a large following throughout Iran because of the wide dispersion of Azerbaijanis who trace back their family roots to the northwest province that is Shariatmadari's base.

Apparently shaken by the latest clash in Tabriz, Shariatmadari wept at a prayer session in the holy city of Qom Friday when he told about 300 followers, who were also crying, that the current Khomeini regime was in many ways similar to the government of the shah.

"Under the shah I was not free to speak and they came to my house and killed a student," the religious leader said. "Under this government I am still not free to speak and they come to my house and kill a guard."

The latest disturbance in Azerbijan began Thursday afternoon when a wooden platform from which Ayatollah Syaed Assadallah Madani offers Friday prayers was burned. Because Madani was appointed by Khomeini, the burning was seen as an anti-government protest.

Later that day, 12 revolutionary militiamen drove up to the Moslem People's Republican Party headquarters. According to a spokesman for the militiamen, the guards were merely trying to investigate the prayer platform burning when they were forced out of their cars into the party building.

Accounts of the rest of the story vary. The militiamen claim they sent reinforcements to rescue their colleagues, but met with intense armed resistance throughout the night.

Party members say they heard three shots outside the headquarters Thursday night. When they went to check, they discovered the militiamen in cars and brought them into the building for further questioning. Three escaped.

"As soon as we got into the room," said party commander Hushang Karimi, "the phone rang. I picked it up and someone said, 'You're surrounded.' As soon as I put down the phone, the shooting started.

Everyone agrees that when the batle ended at 6 a.m. Friday, five persons were wounded and nine militiamen taken hostage.