Scientists exploded a thermonuclear weapon beneath the Nevada Test Site Thursday, swaying high-rise gambling resorts 110 miles away in Las Vegas with the energy of 11 Hiroshima atomic bombs.

The fifth underground nuclear weapons test announced this year by the United States came two days after the signing of summit accords in Moscow that clear the way for joint superpower nuclear verification experiments in three or four months.The detonation was the third U.S. nuclear weapons test since a group of Soviet scientists arrived at the Nevada Test Site in late April to prepare for verification experiments designed to determine whether the superpowers can measure the exact size of a nuclear explosion.

"The weapon test today was a success," federal Energy Department spokeswoman Barbara Yoerg said.

Yoerg observed the 6 a.m. detonation from the command center, 31 miles from ground zero. She said all radiation from the detonation was contained underground, and "no radiation leaked into the atmosphere."

She said she felt no ground motion at the control point.

Less than a minute after "zero time," an earth tremor spawned by the nuclear explosion reached Las Vegas, the state's most populous city.

"It felt like a gentle swaying. I saw a few of my larger plants moving," said a resident of Regency Towers, a high-rise condominium near the Strip.

No damage was reported, and many Las Vegas residents slept through the blast.

Previous U.S. weapons tests in 1988 were announced Feb. 15, April 7, May 13 and May 21.

The last two detonations, considered smaller than Thursday's test, measured 5 and 4.5 on the Richter scale, according to the Earthquake Information Center in Golden, Colo.

The nuclear weapon in the latest test was buried 2,000 feet beneath Pahute Mesa, a 7,000-foot volcanic plateau deep within the boundaries of the Nevada Test Site. The weapon had a yield of less than 150 kilotons, according to the government spokeswoman. The atomic bomb dropped on Hiroshima in World War II was a 13-kiloton weapon.

The weapon was code named "Comstock," after the motherload gold and silver find in Nevada.