MOSCOW, DEC. 9 -- The arms control treaty signed in Washington yesterday was widely hailed here today as both an achievement of Kremlin policy and a welcome sign of improving U.S.-Soviet relations.

From the Communist Party newspaper Pravda to people out doing their errands in 17-degree weather, the signing of a treaty eliminating medium- and shorter-range nuclear weapons was called a landmark event and good news all around.

"It means that we have found a common language and that can only be a good thing," said a middle-aged woman who was out doing her shopping with a friend this morning.

Pravda devoted its first three pages to dispatches from Washington and printed the full text of the treaty as well as of speeches given by Soviet leader Mikhail Gorbachev and President Reagan.

In a commentary, Pravda said the treaty represented a turnaround for Reagan administration policy and could be attributed to the "new thinking" on international affairs that has emanated from the Kremlin.

"New thinking" is the term used for Gorbachev's more pragmatic approach to foreign policy. Pravda said it had created a more constructive atmosphere in the world and "opened the way" for the treaty signed yesterday.

"And although so far it only concerns 4 percent of the U.S. and Soviet nuclear arsenals, this step contributes to strengthening security for the planet overall and reduces the fear of a nuclear catastrophe among European nations," it said.

Pravda pointed out that interest in the summit is running high in Washington. It said it counted 21 summit-related stories in Monday's Washington Post and quoted a recent U.S. poll that showed 66 percent of Americans favorable to Gorbachev.

At a news conference at the Foreign Ministry this afternoon, Oleg Bogomolov, head of the Institute on the Socialist World Order, an influential Soviet think tank, said the significance of the treaty "cannot be overemphasized."

"The Soviet-American agreement testifies to the need for serious improvement in the international climate and the absolute necessity of improving relations between socialist and capitalist countries," he said.

The signing ceremonies, shown on television here late yesterday, drew a wide audience, judging from remarks by a dozen people interviewed in a Moscow park this morning. Of the 12 interviewed, only two had not watched the event and of those, one was on his way to buy a television set today.

"I think it is excellent," he said as he went to the store with his father. "At last they have begun the process of disarmament -- this time I hope for real." His father, who saw the event, clasped both hands together: "Let's hope it keeps going."

Several people interviewed were struck by the warm and pleasant atmosphere at the White House yesterday. "President Reagan was very good, very human," said one elderly man. "He can joke, and that's good: 'trust, but verify,' that was a good one," he said.

People's enthusiasm for the event went beyond politics to the simple enjoyment of watching a good show, complete with Marine bands and gleaming chandeliers. Gorbachev's easy style struck many as a national asset: several, for instance, approved of his informal, friendly gesture when he veered off to shake hands with an unseen figure in a White House hallway. "He seemed to feel at home," said a 32-year-old Russian.

The particulars of the treaty on intermediate nuclear forces drew little comment from the public today, although the text of the agreement was printed prominently in all major newspapers this morning. The government's evening paper, Izvestia, gave a detailed rundown of the clauses on verification, noting that the procedures make the treaty unprecedented in the history of either country.

The Izvestia article also noted that the treaty carefully balances the interests of both sides -- "not the arithmetical balance of forces but the more complicated and important balance of mutual interests."

At a news conference this morning, a general from the Soviet general staff, in response to a question, warned the North Atlantic Treaty Organization against increasing deployment of nuclear-capable strike aircraft in Europe as a response to the elimination of medium- and shorter-range weapons.

"We are not working on any such plan," said Gen. Yuri Markelov, deputy chief of Soviet armed forces information. "And our idea is that NATO should abandon that plan as well. Otherwise, there will be another spiral in the arms race."

At the other end of the political spectrum, Soviet dissidents said they saw the results of the summit so far as a hopeful sign, but worried that "nice words" were being undercut by troubling signs of a crackdown against unofficial opinion at home.

About 20 organizers of a seminar on human rights, set to open here Thursday, have been warned by local officials that their gathering violates a city ordinance banning unauthorized meetings.