Iraqi warplanes fired poison gas at Kurdish civilians trapped in a mountain ravine and killed 2,400, a Kurdish rebel spokesman said Friday.

Word of the alleged slaughter on Aug. 30 was delayed because it took the handful of survivors 10 days to reach southern Turkey and contact rebel officials, the spokesman for the Kurdistan Democratic Party reported.The spokesman said the survivors were fleeing an Iraqi military offensive by trekking to Turkey.

He spoke to The Associated Press in Nicosia by telephone from a West European city. The official, known to the AP, asked that his name and location not be disclosed for "security reasons."

There was no independent confirmation of the reported gas attack. The spokesman said the casualties raised the number of Kurds killed by Iraqi chemical weapons since early August to about 4,300.

The official also said Kurdish guerrillas, battling an estimated 60,000 Iraqi troops pushing into rebel-held mountains in northern Iraq, killed 140 Iraqi soldiers in a major clash several days ago.

"They were all carrying gas masks," he said. "If, as the Iraqis claim, they are not using chemical weapons against our people, who were these soldiers carrying gas masks?"

Iraq's Defense Minister, Gen. Adnan Khairallah, told a news conference in Baghdad Thursday that his forces did not use poison gas against the Kurds in an operation he said was carried out Aug. 27-Sept. 5.

U.S. officials have said they have evidence that the Iraqis have used chemical weapons, outlawed under a 1925 Geneva treaty, against the Kurds.

The guerrilla spokesman said the civilians killed in the Aug. 30 gas attack were 430 families from the Sheikan district of Mosul province in northern Iraq.

About 40,000 Kurds are besieged in Sheikan by Iraqi forces, he said.

The spokesman said the families were cut off by advancing Iraqi troops who moved between them and the border.

"They sheltered in a narrow valley called Bazi in the Mateen mountains nine miles south of Kanimasi in the Amadiyah district," he said.

Six Iraqi jets dropped poison gas on them twice, "and nearly all of the people were suffocated," he said. "A few survivors managed to escape . . . the massacre."