MOSCOW, OCT. 1 -- Soviet leader Mikhail Gorbachev, saying he expected his coming summit meeting with President Reagan to cause a "peaceful chain reaction" that could lead to a series of arms agreements, today proposed new talks between NATO and the Warsaw Pact to curtail military activity in the northern European seas.

Speaking in the Arctic port city of Murmansk, Gorbachev said he saw "signs of improvement" in international affairs and outlined his concept of a "military detente" encompassing the Baltic, North, Greenland and Norwegian seas.

"Favorable trends are gaining in strength in interstate relations," he said. "The substantive and frank East-West dialogue . . . has become a characteristic trait of contemporary world politics."

Gorbachev's optimistic assessment was his first public comment on the state of East-West relations since Washington and Moscow reached an agreement in principle on a treaty to eliminate medium- and shorter-range nuclear weapons more than two weeks ago. Gorbachev, 56, returned from vacation late last week and made his first public appearance in 52 days on Tuesday.

In his proposal, Gorbachev said the Soviet Union would consider removing nuclear-armed submarines from its Baltic fleet and reviewing its nuclear testing range at Novaya Zemlya if discussions proceed on the creation of a nuclear-free zone in the region.

He also proposed opening North Sea shipping lanes to foreign traffic, with routes cleared by Soviet ice-breakers, "depending on progress in the normalization of international relations."

Gorbachev's two-hour speech in Murmansk, which today was honored as having played a heroic role in World War II, was shown live on national television, and was supplemented by coverage on the evening news of his meetings with residents and factory and dockworkers in the northern seaport.

The speech, with domestic and international themes, sought to reassure listeners of the progress of Gorbachev's reform campaign, known broadly as perestroika, or restructuring.

Gorbachev said the reform process had attracted the interest of millions of people abroad, and he said that "anti-Soviet attacks" were being ignored by those engaged in business and political contacts with Moscow.

"This confirms the fact that we are dealing with yesterday's rhetoric, while real-life processes have been set into motion," he said. "This means that something is indeed changing. . . . It is now hard to convince people that our foreign policy {is} mere propaganda."

Gorbachev said the Reykjavik summit, held a year ago, was the "turning point" that led to last month's agreements in Washington. He also said that the Soviet Union's unilateral moratorium on nuclear testing had produced results. "Full-scale talks on these problems will soon be started," he said. "It is obvious that our moratorium was not in vain."

But he also charged that reactionary forces are still arrayed against any Soviet success, and he quoted recent U.S. congressional testimony that advocated speeding up the arms race to weaken the Soviet economy. "We cannot but take into account such a stance," he said.

Gorbachev told his audience of Murmansk party and civic leaders that the Politburo believes the reform program has now reached a "critical" phase. He noted that the foundations of the program have been laid, and said that the task now is for everyone to put it into practice.

Using charts, statistics and graphic examples, Gorbachev tried to allay what he acknowledged are widespread anxieties about pending price increases, a key element in the current long-term economic reforms.

He said the subject of prices had come up at each of his stops -- a reflection of the popular discussion that has also been seen in the Soviet press.

Gorbachev indicated he would not back down from the principle of price reform, but stressed that it would be preceded by wide public debate and by a package of compensatory measures to soften its economic impact.

He noted that heavily subsidized prices for staples such as bread and meat had cost the state 57 billion rubles ($90 billion at the official exchange rate) so far this year, and that they had fostered "disrespect" for the product, to the point where bread was used to feed livestock and even as footballs by young people.

Gorbachev also defended plans to cut down on the size of the huge Soviet bureaucracy. Some Moscow-based ministries face staff cutbacks of as much as 50 percent this fall, according to Soviet sources.

He noted that one-sixth of the Soviet workers are managers, and that management costs add up to 40 billion rubles a year.

He said bad habits had built up over the past years, to the point where many people had become psychologically used to stagnation.