MOSCOW (AP) _ The Soviet Union conducted an underground nuclear test on Sunday on a northern island above the Arctic Circle.

The official Tass news agency said the test on Novaya Zemlya was conducted ''with a view to upgrading military technology.''

Tass said the explosion had an explosive force of between 20 and 150 kilotons. One kiloton has the force of 1,000 tons of TNT.

It gave no other details.