MOSCOW, NOV. 7 -- A marcher standing across Red Square from President Mikhail Gorbachev fired two shots from a sawed-off shotgun today during a Revolution Day parade that also was marked by calls for the Soviet leader's resignation.

No one was injured in the shooting, which took place shortly after Gorbachev returned to his position on top of the Lenin mausoleum after mingling with demonstrators celebrating the 73rd anniversary of the Bolshevik revolution. Security officials said a policeman jumped on the gunman, forcing him to fire one shot into the air and a second into the ground.

KGB chief Vladimir Kryuchkov told reporters at a Kremlin reception that the gunman, identified only as a man from Leningrad who was born in 1938, was "probably mad." A dozen security police immediately seized the man, carrying him away by his arms and legs as he struggled fiercely.

The shooting was the most dramatic incident in a day of demonstrations and counter-demonstrations across the Soviet Union that reflected the deepening divisions in Soviet society. In Moscow, several hundred hard-line Communists infiltrated the official parade, waving portraits of former dictator Joseph Stalin along with banners accusing Gorbachev of betraying socialism.

An hour after the official parade ended, about 10,000 radicals staged their own procession through Red Square to denounce the Communist system and call for Gorbachev's resignation. The anti-Communist march was briefly led by the populist president of the Russian republic, Boris Yeltsin, who earlier had joined Gorbachev and other Soviet leaders in the official reviewing stand on top of the mausoleum.

Video tape taken immediately after the shooting incident showed that the gunman fired from a spot about 80 yards from the Lenin mausoleum, on the opposite side of Red Square, near the GUM department store. Witnesses said that the man, who concealed the double-barreled shotgun under a blue coat, had joined a group of marchers representing the Bauman district of Moscow.

The shooting was a startling reminder of the surge in violence that has accompanied Gorbachev's perestroika reform program. It was the first incident of its kind since January 1969, when a young army lieutenant standing outside the Kremlin fired 16 shots at a limousine that he erroneously thought was carrying Leonid Brezhnev, then the Soviet leader.

On this occasion, there does not seem to have been any real physical threat to Gorbachev, who was separated from the gunman by several ranks of security men.

A cameraman who filmed the incident for the official Soviet news agency Tass said he thought the man was probably deranged, as he had little chance of shooting accurately at such a distance with a sawed-off weapon. Foreign journalists and diplomats in a reviewing stand next to the mausoleum could clearly hear the shots, which rang out across the square within two seconds of one other. But there appeared to be no signs of panic among the leadership and the march past the reviewing stand by tens of thousands of Communist Party activists continued as scheduled.

In a short speech at the beginning of the parade, Gorbachev acknowledged that the "renewal process" in the Soviet Union had proved "much more painful and dramatic than could have been expected." He said the entire country was alarmed by shortages of basic consumer commodities, spiraling prices, rising crime and ethnic conflicts.

"But we must not panic, or even less call for the turning back of the clock," said Gorbachev, who combines the posts of head of state and Communist Party leader, rebuffing hard-line Communists who have called for a crackdown on dissent.

Many marchers in the hour-long official demonstration carried slogans expressing dissatisfaction with the results of Gorbachev's reform program. One typical banner showed a naked man feeding off bones, with the slogan "Stop the experiment, Mikhail Sergeyevich." Another said, "Gorbachev, we have no meat, no butter and no peace."

Banners carried by the contingent of hard-line Stalinists included one that said, "Anti-Communist Gorbachev, get out of the Communist Party," and another accusing Yeltsin of being on the CIA payroll. "Gorbachev, we have no meat, no butter and no peace."

-- banner carried by demonstrator

Others had a distinctly antisemitic flavor: "Zionism is Jewish fascism" and "No to Zionism on Russian land."

Moscow's reform-minded Communist Party chief, Yuri Prokofiev, later told reporters that Gorbachev had found some of the slogans reactionary and was disturbed by them. During the May Day parade earlier this year, the Soviet leader was booed off the mausoleum by radicals who carried banners denouncing the Bolshevik revolution as a national catastrophe.

Soviet leaders had attempted to prevent today's parade from being marred by protests by calling for a ban on all unofficial demonstrations. But the appeal from the presidium of the Supreme Soviet legislature was widely ignored by radical-controlled city councils across the country.

The military portion of today's parade in Red Square featured the first public appearance of the SS-25 mobile intercontinental missile, a strategic weapon deployed since 1985. Twelve of the 60-foot-long, single-warhead weapons, which the Pentagon says have a range of 6,500 miles, passed the reviewing stand on 14-wheeled transport vehicles.

During the parade, Gorbachev was seen chatting briefly with Yeltsin, who is widely regarded as his main political rival. The Russian president earlier told reporters that he had agreed to meet with Gorbachev on Sunday to discuss their differences over the pace of economic reform and other issues.

At a Kremlin rally Tuesday, one speaker called on the two leaders to work together, saying that their quarrel is harming the Soviet Union's chances of getting out of its present crisis. "Both of them must realize that future opposition makes them both less popular," said Leonid Bliznov, a member of the Supreme Soviet.

In several cities, including the Ukrainian capital, Kiev, demonstrators had announced that they would prevent today's military parades from taking place by lying down in front of tanks. But order was maintained by large contingents of security men.

In Vilnius, the Lithuanian capital, local police clashed with Soviet paratroops who stormed a conservatory after students mocked a military parade, the independent Baltic News Service reported.