The Kurdistan Democratic Party said today that fierce fighting has resumed in northwestern Iran, with the Iranian Army joining Turkish-speaking Azerbajijanis and Islamic militiamen against the region's Kurdish tribesmen.

Tehran-based spokesman for the party told a hastily convened news conference tonight that the opposing forces broke a cease-fire agreed to Monday.

"The Turks, Mojaheds [Islamic militiamen] and Army forces violated the cease-fire and are advancing into Kurdish territory, provoking the population and worsening the situation beyond all control," the spokesman, Jalil Gadani, said.

He said 500 people have been killed in and around the West Azerbaijan provincial town of Naqadeh since fighting broke out there Friday. He said the Army was using tanks and helicopter gunships to help the Turks and Islamic militiamen attack Kurdish villages.

"What we forsee is that the government, the Army, the Mojaheds and the Turks are going to unite into one force and wage war on the Kurds," Gadani said.

Gadani's statements corroborated the impressions of foreign correspondents who visited the area that the Army units sent to Naqadeh were decidedly proTurk and were working closely with the Azerbaijani residents against the Kurds. The troops at Naqadeh seemed to be predominately Azerbaijani Turks themselves, the correspondents said.

Gadani's other allegation-that the Army used tanks and helicopter gunships against Kurdish villages-could not be independently confirmed, however, although visitors did see flames and smoke rising from hwat were said to be burning Kurdish homes.

Gadani said Kurdish homes were looted as well as burned, and he charged that the Army and the Turks were holding hundreds of Kurds hostage.

He said helicopters today attacked the village of Aliabad near Oshnovieh, killing six Kurdish civilians and wounding four.

He charged that Turks kidnaped four Kurdish families from the village of Dalmeth.

Iran's state-run radio said food shortages and epidemics were feared in the predominately Kurdish city of Mahabad 35 miles south of Naqadeh because of a large influx of Kurdish refugees driven out of their homes by the Turks. Earlier the radio had reported that the water of a river flowing through Naqadeh was polluted and should not be used for drinking. There was speculation that victims of the Naqadeh fighting had been dumped into the river.

A doctor who arrested in Tehran from Mahadbad today was quoted as saying an entire Kurdish village was wiped out in the recent fighting and that the border between Iran's Kurdistan and West Azerbaijan provinces is "very tense."

"Mahabad is normal but arms are in wide circulation," he told reporters. "Every Kurd above the age of 14 is armed-everybody."

The doctor adeed, "Every Kurd seems to be in shape for battle any time of the day or night. People are selling their carpets, pots and pans to buy arms." He said Soviet-made Kalashnikov automatic rifles were going for a little more than $100 apiece.