BEIJING -- Chinese troops of the People's Liberation Army opened fire with automatic weapons early today on huge crowds of civilians in Beijing, killing at least 100 of them and perhaps many more, according to medical and diplomatic reports, in a successful effort to recapture Tian An Men Square from pro-democracy demonstrators.

At least 400 people were reported wounded.

For China, it was a fundamental turning point. The Communist Party leadership headed by the aging Deng Xiaoping made the decision that no matter how high the costs to its image at home or abroad, it had to overwhelm with a force the students and other demonstrators who had challenged the power and legitimacy of the regime.

The gunfire began shortly after midnight and continued until well after dawn. There was gunfire all over Beijing, from the central Tian An Men Square area to the areas outside the main tourist hotels to the outskirts of the city.

At times, the firing was indiscriminate. At about 5:30 a.m. today, for example, a military convoy of about 100 vehicles--including tanks, armored personnel carriers, trucks and jeeps--swept past the Beijing Hotel toward Tian An Men Square, firing at bystanders.

After they reached the square, at about 5:45 a.m., heavy automatic rifle fire could be heard from the area, which had already been subjected to several other lengthy volleys earlier in the morning.

Crowds Won't Disperse

At noon today, the troops had cordoned off Tian An Men Square, but crowds of Chinese refused to disperse. And the shooting in the square had still not subsidied.

Every hour or so through this morning, troops fired volleys of gunfire in an apparent attempt to intimidate the crowds. Each time they did so, at least 1,000 people or more fled from the area of Tian An Men Square. Yet other Chinese kept pouring into the square, many of them to resist the troops and some of them merely to see what was happening.

There had been more than 100,000 Chinese civilians in the square to look at or join the demonstrators for democracy on a balmy Saturday evening. When the troops arrived and the firing began, many of them rushed out in panic.

"Duo si le, duo si le," several of them shouted. "Many have died, many have died."

It was impossible to say exactly how many were killed, but by all indications, the death toll was huge.

When one line of troops crouched and opened fire on a crowd at Tian An Men Square shortly after 3 a.m., an American reporter saw about 50 people go down.

Even after the shooting began, hundreds, perhaps a few thousand Chinese were said to have remained in the downtown area, saying they were prepared to die for the cause of democracy, the cause for which they began their series of demonstrations at Tian An Men seven weeks ago.

Guns Heard Near Newspaper

The deaths occurred not only in the center of the city, but in outlying areas. One foreign eyewitness heard firing shortly after dawn outside the compound of the Communist Party newspaper, People's Daily, in northeastern Beijing. He was told that four people had been killed.

Hospitals in the area were so full of casualties that they scarcely had time for those who were not severely wounded.

A U.S. Embassy official said that there were about 70 dead and 300 wounded at People's Hospital in western Beijing. Another eight dead and 80 wounded were reported at Beijing University Hospital, and there were at least seven dead at the Second Hospital of Beijing.

Casualty Estimates Vary