MOSCOW -- Pro-Communist demonstrators, turned awa from Red Square on May Day, charged into a line of riot police with bricks and makeshift staves yesterday, setting off an hourlong battle that injured more than 150 people.
The battle on Gagarin Square, under a tall monument dedicated to the first man in space, was the worst political violence here since the August 1991 coup. It was broken up with water cannons and police on horseback.
Later, spokesmen for both President Boris N. Yeltsin and his critics called the clash largely inevitable.
Mr. Yeltsin's supporters saw it as the opposition's last desperate stand after losing in last Sunday's national vote of confidence. But the president's opponents said Mr. Yeltsin's insistence on a referendum caused such a deep split in society that only blood could flow from it.
Protesting on communism's most important holiday, about 2,000 people were marching along Lenin Avenue when they came up against police armed with shields and billy clubs. The protesters' front ranks were filled by tough-looking men, unusual for these gatherings.
Stopped under a festive banner put up by the city that read, "To the Holiday, Dear Russians," the crowd began tearing pieces of crumbling walls, throwing chunks of concrete and brick. They used the poles that had borne their red flags to beat policemen. Even the elderly joined in, gathering ammunition.
Seventeen policemen were hospitalized, officials said. They were among 80 policemen and 70 demonstrators reportedly injured. Two trucks and a car were set afire.
A policeman was seriously injured when he was caught between two trucks, a police spokesman said.
In a statement, Mr. Yeltsin's spokesman, Vyacheslav Kostikov, sounded an ominous note.
"It has become known that the organizers of the attack regard today's action as the beginning of a campaign of resistance to the lawful democratic authorities," he said.
"The bloody violence . . . puts its organizers and the parties and groups that stand behind them in face of a serious legal responsibility."
A spokesman for Mr. Yeltsin's chief critic, Ruslan I. Khasbulatov, the speaker of Parliament, fought back, implying that Mr. Yeltsin had provoked the battle as an excuse to assume new powers.
"This event is other evidence of the split of society, which was deepened by the recent referendum held at the initiative of the president of the Russian Federation," said the spokesman, Konstantin Zlobin.
"The [Parliament] and all sensible people repeatedly warned about the disastrous consequences," he said. "It is clear that these events are needed by those who will stop at nothing, even the shedding of human blood, to find a pretext for using extreme measures aimed at curbing citizens' democratic rights and freedoms."
Prosecution of the leaders of the political parties involved in the demonstration was reportedly under consideration last night.
Emotions had been running high here since the bitterly fought referendum, particularly among extremists like those involved in yesterday's march. Among them was Ilya Konstantinov, a leader of the National Salvation Front, a rabid anti-reform group that Mr. Yeltsin tried unsuccessfully to ban.
Mr. Konstantinov called the confrontation a "deliberate provocation aimed at paralyzing any resistance."
The opposition was undaunted, he said. "Today marks the beginning of real resistance," he said. "Motherland or death."
For the first time, May Day demonstrations were forbidden on Red Square, although about 5,000 protesters organized by labor unions were allowed to gather nearby.
The demonstrators who clashed with police were led by the anti-reform, pro-Communist Russian Labor Party.
The demonstrators had been given a permit to assemble yesterday morning near Oktyabraskaya Square, about a mile and a half from the Kremlin and Red Square.
Joined by Viktor Anpilov, the leader of the Russian Communist Workers Party, they discussed marching to Red Square anyway, then decided to go in the other direction to the Lenin Hills overlooking the city.
Three members of Parliament rode in a truck at the head of the march -- Mr. Konstantinov, Mikhail Astafyev and Gennady Sayenko. They were accompanied by two of the men accused in the August 1991 coup, Gennady Yanayev, then the vice president of the Soviet Union, and Vladimir Kryuchkov, former head of the KGB.
The truck carried posters of Lenin and Stalin and a poster that read, "All Power to the Soviets!"
Mr. Kryuchkov told Interfax that the Red Square ban was an "irrational measure which suggests that the authorities are nervous."
The battle with police was joined just before noon at Gagarin Square, under the steely gaze of a huge monument to the space hero Yuri Gagarin that stands 40 feet tall on a 90-foot-high fluted column.
Nikolai Boiko, a police spokesman, said some demonstrators were arrested, but probably not any of those who had inspired the fighting. "These people do not hurl stones," he said. "Others do it for them."
By late afternoon, the square was empty and littered with debris while marchers gathered around the Russian Parliament building. There, hundreds of police -- some wearing bulletproof vests and many carrying shields -- looked on, but no violence was reported.
Elsewhere, the city was largely deserted. The Communist May RTC Day holiday has been turned into a rite of spring. Nearly everyone has a four-day weekend, and anyone who can manage has gone to the countryside to begin turning over the dirt in the garden, picnic, drink vodka and generally forget about the problems of everyday life.
Anyone who couldn't manage to get away appeared to be gathered in Gorky Park, strolling in the sunshine and eating cotton candy.