WASHINGTON -- A deadly bunker-busting bomb built on a principle roundly denounced by Human Rights Groups in the past was used by U.S. forces for the first time in Afghanistan Saturday, a military official acknowledged.

The thermobaric bomb BLU-118S was among the more than 80 pieces of ordnance dropped by U.S. warplanes south of the Afghan city of Gardez where intelligence had discovered a concentration of Taleban and Al-Qaeda fighters.

"We used one thermobaric bomb in that operation," Navy Lieutenant Commander Matthew Klee, a spokesman for the Central Command, told AFP. "It was the first time we used it."

The bomb, which belongs to the category of so-called fuel-air munitions, is capable of penetrating deep underground to reach hidden command bunkers or caves and explode upon hitting its target, according to experts and defense officials.

Its explosive charge is designed in a way that allows the attacker to practically pulverize all occupants of the underground structure.

"It works as a combination of a shock wave and a fuel explosion," Klee explained. "The first explosion spreads flammable aerosols through the underground complex. Then, the second ignites the fuel."

According to independent experts, the bomb, once detonated, produces rapidly expanding shock waves flattening anything near the epicenter of the aerosol fuel cloud, and capable of causing extensive damage far beyond the immediate strikes area.

In addition, shock waves produced by the BLU-118S are capable of navigating underground labyrinths and literally leaving no stone unturned, according to Klee.

"When the shock wave from a normal bomb hits a wall it stops," said the spokesman. "With BLU-118, the shock wave goes around the corner."