SEOUL, South Korea - In a case that has sparked the largest anti-American rallies seen here in years, an Army sergeant was acquitted yesterday in a U.S. military court of criminal negligence in the deaths of two South Korean girls who were crushed by a 50-ton armored vehicle.

Sgt. Fernando Nino, the vehicle's commander, was found not guilty of negligent homicide in the deaths of Shim Mi-son and Shin Hyo-soon, both 14, who were hit on a narrow road north of Seoul. Today, a military jury will hear the case of the vehicle's driver, Sgt. Mark Walker.

The acquittal was immediately protested by South Korean activists who have demanded that the U.S. command surrender the sergeants to South Korea's judicial system. The activists promised a wave of demonstrations "until justice is done."

"The jury was only composed of U.S. soldiers," Shim Su-bo, father of Shim Mi-son, told The Korea Times yesterday. "The trial was not fair."

The U.S. command, sensitive to anti-American feelings engendered by the case, took the unusual step this week of opening the court-martial to Korean reporters and family members.

Minutes after the sergeant was acquitted, Lt. Gen. Charles C. Campbell, commander of the 8th U.S. Army, issued a statement that began with condolences for the deaths of the girls, who were run over by the vehicle during a training exercise in June. He also defended the military justice system.