Iran radio tonight reported that army and air force units had launched an attack on Kurdish positions around the western Iranian town of Mahabad, the center of resistance for the autonomy-seeking Kurds.

Heavy fighting was going on outside the town, the official radio quoted a military spokesman as saying.

The spokesman also said the army had taken over from the Kurds the border town of Piranshahr and spoke of heavy casualties in other action by the army in the border area.

Kurdish sources, however, rejected the official reports, saying the fighting has been concentrated around the town of Miandoab, northeast of Mahabad, with tanks supported by three helicopters and jet fighters attacking Kurdish positions. Witnesses said that rebels repelled 400 Iranian soldiers that had attempted an advance on Mahabad.

The attacks came less than 24 hours after Interior Minister Hashem Sabbaghian gave in a radio and television broadcast what he said was "probably the last warning" to the Kurds to surrender.

Iran's de facto head of state, Ayatollah Ruhollah Khomeini, has in the past week repeated his instructions to the armed forces to crush the Kurdish insurgents and execute their leaders. Large columns of tanks have been reported moving toward Mahabad in recent days but until today had held back from launching any attack on the Kurdish stronghold.

First Kurdish reports spoke of an attack by 26 tanks but other Kurdish sources later said that only 17 were involved and that six of these had been knocked out and the advance by the army halted.

The Kurds in Mahabad also reported Air Force jets making a number of high-speed passes over the town but said the jets had not attacked.

Earlier in the day, Kurdish gunmen killed 15 Revolutionary Guards and injured three more in an attack on a vehicle carrying them to the northwest of Mahabad. The news agency Pars said another six persons were killed in a grenade explosion in Naghadeh.

In his broadcast last night, Sabbaghian also accused Irag of providing refuge and aid for Iranian Kurdish rebels.

"Iraq's border is open to Kurdish rebels," Sabbaghian charged. "Tents have been set up on the other side of the border where insurgents are received and served."

The Iranian Kurds, Sabbaghian said, were armed with tanks, armored personnel carriers, armored cars and anti-aircraft guns that had been sent from abroad.

"Israel is providing them," he charged.

Government spokesman Sadegh Tabataba charged in a television interview that foreign countries were arming the Kurds. He also said leading Western news agencies were "Zionist-led," and accused them of false reporting of events in Kurdistan.