MECCA, SAUDI ARABIA, JULY 2 -- About 1,400 Moslem pilgrims were trampled to death or died of suffocation today in a stampede in a pedestrian tunnel leading into the Islamic holy city of Mecca, witnesses and diplomats here said.

They said the stampede apparently began when hundreds of pilgrims stopped in the middle of the 500-yard-long air-conditioned tunnel to escape the 112-degree heat outside and were caught in the crush of hundreds of others pushing to get in. Some witnesses said also that the tunnel ventilation appeared to have stopped.

More than 18 hours after the disaster, Saudi officials had not given a death count. The official Saudi news agency SPA said the interior minister would issue a statement Tuesday to clarify the number of dead.

Diplomats who declined to be identified put the total death toll at 1,400 or more and said most victims appeared to be Malaysians and Indonesians, while the Saudi Interior Ministry said only that there were "some deaths and some cases of fainting."

State-run Saudi radio said ambulances and security forces rushed to the exits of the tunnel, which joins Mecca and the pilgrim tent city of Mina. Witnesses said people continued to pour into the tunnel despite the screams of those trapped and injured inside.

People were smothered "as thousands of the pilgrims thronged through the tunnel, causing severe congestion within the tunnel as the pressure was beyond its capacity," the radio broadcast said.

One witness said the flow of people through the tunnel, which can accommodate an estimated 1,000 persons, stopped suddenly, and the crowd inside quickly swelled to at least 5,000. "With the lack of oxygen, a good number collapsed unconscious, and some died," he said. The witness said he helped carry victims to waiting ambulances but that it was impossible for him to determine how many people were dead or simply unconscious.

It was apparently the worst accidental loss of life ever in the holy city and came at the end of the Moslem Feast of Sacrifice, shattering what had been an uneventful observance of the annual Moslem haj, or pilgrimage, for which about 2 million Moslems had journeyed here.

But Mecca has been no stranger to violent death in recent years, as Moslem fundmentalists and rival Islamic factions have clashed here.

During the 1987 haj, Iranian Shiite Moslem pilgrims battled Saudi security forces, leaving more than 400 people dead, and hundreds more injured. The year before, the Saudi police confiscated large quantities of explosives from members of the Iranian contingent to Mecca.

In 1979, heavily armed religious extremists seized the Grand Mosque and held it for two weeks before Saudi forces stormed it. More than 250 people were killed, and Saudi authorities later beheaded 63 more.

Saudi Arabia restricted the number of pilgrims and broke off diplomatic ties with Iran after the 1987 fighting, the most serious of a series of incidents involving Iranians here since Iran's Islamic revolution of 1979.

The incidents were fired by Iranian efforts to politicize the haj and encourage other Moslem nations to seize control of shrines at Mecca and Medina from the Saudi royal family.

Last month, the Saudi government said Iranians would be welcome to take part in this year's pilgrimage but would not be allowed to demonstrate.

In July of last year, two bombs exploded in the city as hundreds of thousands of pilgrims were praying and walking around the Kaaba, Islam's holiest shrine, inside the Grand Mosque. One person was killed and 16 wounded in blasts, which were believed connected with the centuries-old feud between Sunni and Shiite Moslems over the successor to the prophet Mohammed. Sixteen Shiites were convicted in the bombings and executed.

Every Moslem has a religious duty to make the pilgrimage to Mecca, the birthplace of Mohammed, and to Medina, where Mohammed is buried.