MOSCOW, OCT. 24 -- The Soviet Union staged an underground nuclear test today, its first in a year, in the Arctic archipelago of Novaya Zemlya, the government news agency Tass reported.

The blast had a yield of between 20 and 150 kilotons, the official news agency said, adding that "it was set off to confirm the reliability and increase the safety of nuclear weapons."

It was the first Soviet nuclear test reported since an explosion of between 20 and 75 kilotons in October 1989 at the Semipalatinsk test range in the central Asian republic of Kazakhstan.

Radiation levels around Novaya Zemlya were normal after today's test, Tass said.

The Novaya Zemlya test range, which had not been used for more than a year, was the target of an antinuclear protest this month by Greenpeace, an environmental group, which expressed concern that testing might be moved there from Kazakhstan.

A ship belonging to Greenpeace was boarded by Soviet border guards and expelled from Soviet waters near the islands.

The Nordic countries also have expressed concern about possible resumption of tests at Novaya Zemlya, about 375 miles east of Norway.

But Moscow is also under pressure not to resume testing in Kazakhstan, where an environmental movement has held demonstrations.

Last November, the republic's legislature appealed to the Kremlin to stop the explosions. The Soviet Union frequently has urged a stop to nuclear testing.

This month, Deputy Foreign Minister Vladimir Petrovsky proposed a vote on nuclear testing by elected legislatures around the world.

He told the U.N. General Assembly Oct. 9 that the Soviet Union had not conducted any tests since October 1989 and was prepared to extend that ban indefinitely if the United States would do the same.

The Soviet legislature and the U.S. Senate recently approved two U.S.-Soviet nuclear test limitation treaties that were negotiated in the 1970s but delayed by concerns over possible cheating.

One of them, the 1974 Threshold Test Ban Treaty, lowers the explosive force of permitted underground nuclear explosions to the equivalent of 150,000 tons of TNT.