The Soviet Union said today that President Reagan's decision to produce the neutron weapon is "another extremely dangerous step" toward intensifying the arms race and "enhancing the threat of nuclear war."

In an authoritative commentary evidently approved at the highest levels, the official news agency Tass said, "All signs indicate that this is in line with Reagan's new strategy designed to justify the admissibility of a limited nuclear war and condition people to this horrible thought."

Official reaction to the announcement generally was muted in Western Europe, with governments there underlining the U.S. decision to store the weapons at home and deploy them in Europe only after consultation. The prospect of their being stockpiled in NATO nations provoked intense debate in the past.

Scandinavian officials criticized Reagan's decision and West German newspapers charged that the Europeans should have been consulted. A Bonn spokesman said the government was informed but the production decision was strictly a U.S. matter.

Tass said the Soviet Union "cannot remain an indifferent bystander" to the U.S. decision "and will have to give such a response to the challenge that will be demanded by the security interests of the Soviet people and their allies."

The Soviets see the neutron weapon as a major threat to their tank divisions, which are the mainstay of Soviet land forces. As an enhanced radiation device, the neutron weapon is designed to kill troops but leave surrounding buildings intact. Western military specialists say the weapon could effectively neutralize the current Soviet numerical advantage in tanks available for conflict in central Europe.

Tass called the neutron device "the most inhuman type of weapon of mass annihilation" and said that "the same cannibalistic instincts prevail now in the White House" as when president Harry Truman ordered the use of atomic weapons against Japan in 1945.

But the Tass commentary and other recent pronouncements here appear to be more than just an angry reaction to what the Soviets say is an American drive for military superiority. They seem to reflect a worried perception of a policy drift in Washington in which impulses from the Cold War have gained the upper hand.

In Tass, the Communist Party newspaper Pravda and elsewhere, the Soviets have voiced concern about what they call Reagan's view on the inevitable conflicts between the two superpowers. The Soviets indicate this increases the danger of miscalculation on both sides.

The Kremlin contends that the United States is trying to change the strategic balance by deploying medium-range nuclear missiles in Western Europe and that it also wants to change the balance of conventional forces in the European theater by eventually deploying the neutron warheads.

In a broader sense, Soviet officials in private conversation as well as public pronouncements present Reagan's policies as a radical departure from the understood code in bilateral relations -- which essentially came down to controlling the arms race and avoiding direct military confrontation.

The neutron decision, Tass said, "confirms once again that the prattlings of the U.S. government" about its interests in arms control efforts "is rude deception designed to camouflage the Reagan administration's course for preparing a nuclear war."

The bitter Tass commentary was reminscent of a Soviet press campaign against the original U.S. deicsion in 1977 to manufacture and stockpile the neutron device. President Jimmy Carter subsequently rescinded the order after adverse West European reaction.

The Soviets said subsequently that they could produce a neutron device but that they had decided to shelve the production plans following Carter's decision.

In an apparent attempt to generate West European opposition to Reagan's decision, Tass said today that the United States is planning to stockpile the weapon first and then "wrest consent" from NATO allies to station them in Western Europe.

News services added:

In Bonn, government spokesman Lothar Ruehl said possible stationing of neutron weapons in West Germany was not an immediate issue. He said Bonn was informed of the decision but as it was exclusively a matter of U.S. production and stockpiling, Washington had not engaged in consultations. West Germans generated much of the opposition to neutron weapons in the past.

In Frankfurt today, about 50 demonstrators opposed to Reagan's decision tried to block the main entrance of the U.S. Army headquarters and force their way into the building. Thirty were detained for identity checks following scuffles with West German police, a police spokesman said.

The independent Stuttgarter Zeitung newspaper said Reagan was "playing a game the Americans call hardball" by presenting the Europeans with accomplished facts but the conservative Bild Zeitung, owned by Axel Springer, praised President Reagan for making an uncomfortable decision.

While most Western capitals responded with a mixture of deference and no comment to the announcement, Norway filed a protest through the U.S. Embassy in Oslo. Prime Minister Gro Harlem Bruntland told Norwegian television her government had objected on grounds the U.S. decision will hamper East-West arms reduction talks.

A spokeswoman for Prime Minister Margaret Thatcher said she had no comment.

In Sweden, Foreign Minister Ola Ullsten declared: "The United States' decision . . . means a further dangerous and alarming escalation of the recent armaments race between the superpowers."

Denmark's Foreign Minister Kjeld Oleson said Danish opposition is unchanged.

Soviet criticism was not echoed by Peking. The offical New China News Agency reported Reagan's decision without comment.

The United States is not the only nation with technology for making neutron weapons. France's then-president Valery Giscard D'Estaing disclosed last summer that his nation had tested a neutron warhead. There was no official French commment today on the U.S. decision. Socialist President Francois Mitterrand has not announced a decision on producing French neutron weapons.