A controversial and twice postponed U.S. underground nuclear explosion, which may induce the Soviet Union to end its eight-month moratorium on nuclear testing, took place just after dawn yesterday at the Nevada Test Site, a Department of Energy official announced.

Immediately following the announcement of the test, the Soviet news agency Tass called it "another demonstration of the administration's criminal contempt for the calls of U.S. and world opinion to join in the Soviet Union's moratorium," correspondent Celestine Bohlen reported from Moscow.

The low-yield U.S. nuclear device, code-named Mighty Oak, was detonated 1,300 feet below the surface to see how radiation would affect the new warhead for the MX intercontinental missile, parts of the new Trident II submarine-launched missile, including its warhead, and hardware for the new Midgetman missile, according to officials of the Defense Nuclear Agency, which sponsored the test.

Last July, Soviet leader Mikhail Gorbachev announced a moratorium and asked for U.S. participation in an effort to negotiate a ban on underground explosions. President Reagan refused, saying that U.S. tests would continue as long as nuclear weapons are needed as a deterrent to war, to assure the reliability of the warheads in the U.S. arsenal and to develop warheads for new weapons.

Last night, on Soviet television news, political observer Valentin Zorin repeated Gorbachev's remarks of March 29 when the Soviet leader said that U.S. failure to halt its tests would end the moratorium, Bohlen reported.

"We regret it, but we will be forced to do so, since we cannot forgo our own security and that of our allies," said Zorin, quoting Gorbachev.

Last month, after eight U.S. tests while the Soviet Union conducted none, Gorbachev announced that he would resume testing if the United States exploded another weapon after March 31.

A Tass military expert said yesterday's explosion does not mean that the Soviets will end efforts for a ban on all nuclear testing. Gorbachev has said that progress toward such an agreement is one of his goals for the next summit with Reagan.

The U.S. test, planning for which began almost two years ago, had been scheduled Tuesday, the day that Reagan received Soviet Ambassador Anatoliy Dobrynin for his farewell visit and a discussion about the next summit.

The shot was delayed because of technical problems reportedly in electrical circuits, according to sources. A delay Wednesday was attributed to weather, more technical problems and the presence of antinuclear protesters on the 1,300-square-mile test site.

Yesterday, Department of Energy officials said, only 22 protesters were at the site's main entrance when the explosion occurred at 6:08 a.m. PST, two hours earlier than expected. Authorities reported more than 100 arrests during three days of protests at the site.

Another underground test is scheduled next week, and one is planned for April 23-25, informed sources said. The latter is expected to test the reliability of a weapon under production and a new on-site monitoring system called Cortex, used to measure the yield of the explosion.

Last month, Reagan invited Gorbachev to send scientists to the latter test to observe the monitoring device. Reagan said then that acceptance of his invitation could lead toward ratification of the 1974 threshold test ban treaty. In a recent speech, Gorbachev said he would not send observers.

Fifteen U.S. nuclear tests are planned this year, sources said. The first, on March 22, tested a low-yield version of a proposed warhead for the new Midgetman missile, and yesterday's blast was the first of two so-called nuclear-effects tests scheduled this year. The next one of this type is planned in December, according to testimony before Congress earlier this year.

Moves are under way on Capitol Hill to prevent funding further U.S. tests, at least until Soviet tests are resumed.