In an impressive climax to 10 days of antinuclear protests, more than a million people poured into the streets of West Germany today to protest the deployment of Pershing II and cruise missiles scheduled to begin in December.

The huge crowds, described by police as the biggest in West Germany's postwar history, took advantage of balmy autumn weather to participate in rallies across the country that bore the markings of vast festive picnics rather than apocalyptic confrontations.

Similar protests were held in London, Paris, Stockholm, Rome and Vienna, according to The Associated Press.

One of the rare violent incidents was reported in Bad Ems, about 50 miles south of Bonn, where a bomb was tossed over the wall of a military intelligence school. Police said it caused substantial, damagebut no one was injured.

About 6,000 people broke off from 200,000 marchers in Hamburg, smashed windows, started fires and hurled stones at police, AP said.

About 350 people were briefly detained when they surrounded the U.S. Wiley barracks near Stuttgart, but police said they conducted only identity checks.

In Bonn, 400,000 people sprawled across a grassy mall to listen to folk music and speeches by Social Democratic Party Chairman Willy Brandt, Nobel Prize-winning author Heinrich Boell and Greens Party peace activist Petra Kelly.

Most of the protest actions involved innocuous displays of political theater, conducted in a spirit of good-humored cooperation with local police forces.

Early in the morning, about 30,000 protesters formed a star-shaped chain linking the embassies of eight nations that possess nuclear weapons or are believed to have the capacity to make them--the United States, the Soviet Union, France, Britain, China, India, Israel and South Africa.

Members of the Greens Party carried a thread about four miles long between the U.S. and Soviet embassies, where they delivered model telephones to symbolize the need for an effective disarmament hotline between the superpowers.

In Stuttgart, nearly 200,000 people successfully formed a human chain 65 miles long from U.S. Forces European headquarters to American Army barracks at Neu Ulm, which will serve as one of three sites for Pershing II missiles. In West Berlin, another 75,000 people turned up at a rally in the city plaza.

The remarkable lack of violent disturbances was traced by police authorities to superb cooperation with leaders of the peace movement.

"We are grateful for the considerate and extremely peaceful behavior you have shown today," Norbert Schnoor, interior minister for the Westphalia region, told a cheering throng in Bonn.

Unlike previous West German demonstrations that often carried anti-American overtones, the rallies today directed criticism at both superpowers for their role in the arms race. A caravan of automobiles near Stuttgart carrying mock versions of SS20 missiles on roofs drew strong applause as part of the protest.

Other demonstrators in Bonn carried signs that read "Pershing go home" on the front side and "SS20s into the Volga" on the back.

Heinrich Boell also drew attention to the theme that the peace movement "in no way wished to show animosity to Americans." He stressed that more American politicians are speaking out against the deployment.

In what was regarded as the keynote address of the Bonn rally, Nobel Peace Prize winner Brandt endorsed a halt to new missile deployment in order to provide time for further arms control negotiations in Geneva.

He also backed a freeze on nuclear weapons, to be followed by their eventual removal and "a shift in the direction of using resources for a worldwide struggle against poverty, hunger and oppression."

"In this minute, 30 children are dying of hunger and illness while 3.5 million marks $1.4 million dollars are being spent for arms," he said. "This is against all humanity, and it is also ruining the world economy."

"We need in Germany, and in Europe while it stands, not more means of mass destruction but less," he insisted. "This is why we say no to more and more new nuclear rockets."

Brandt did not cricitize the Reagan administration by name, but he asked why Moscow's offer to destroy some SS20 missiles as part of an ultimate arms pact was not seized upon "to reach an agreement that would mean fewer tools of mass destruction in Europe."

Despite his eloquent plea against new missiles, Brandt was criticized harshly by Greens Party leaders for failing to denounce all weapons systems and for not demanding West Germany's withdrawal from the North Atlantic Treaty Organization.

Banners were hoisted during his speech that read: "You hypocrite" and "Willy, nobody belives you anymore."

Petra Kelly expressed deep chagrin after Brandt spoke, saying she had invested great trust in Brandt but now felt betrayed because he did not call for an unconditional rejection of all nuclear missiles.

"We need no weapons at all, not just fewer," said Kelly to roaring applause. "It is absurd for Brandt to say no to new weapons yet yes to NATO."

For their part, members of West Germany's center-right ruling coalition have charged that the Social Democrats have ruptured the long cherished consensus on security and foreign policy.

Foreign Minister Hans-Dietrich Genscher claimed today that Brandt's appearance at the rally proved that his party was in the process of "becoming no more than a left-wing protest movement."

The Associated Press also reported:

In Rome, about 100,000 people marched past the U.S. and Soviet embassies and then sprawled on the ground at St. John Lateran Square in a "die-in" simulating the effect of a nuclear holocaust.

Another 10,000 demonstrators turned out for a march in Paris. In Vienna, 5,000 people formed a human chain linking the U.S. and Soviet embassies and 35,000 rallied at City Hall.

Yet another arm-linking demonstration that included Swedish Prime Minister Olof Palme joined the U.S., Soviet, British and French embassies in Stockholm in a 20,000-strong handshake. Protests were also held in Canada.

The official Soviet news agency Tass said the protests had shown that Western Europe's people reject the "militaristic" attitudes of their governments, AP reported. But in East Berlin, the Communist Party newspaper Neues Deutschland took the unprecedented step of publishing church letters to party leader Erich Honecker condemning new nuclear armament in both East and West.