The former head of state of Cambodia's notorious Khmer Rouge regime, now facing trial for crimes against humanity, has been sent to a hospital. He's the second defendant in the case to be hospitalized this week.

Tribunal spokesman Lars Olsen said 81-year-old Khieu Samphan was hospitalized Wednesday suffering fatigue and shortness of breath. Co-defendant Nuon Chea, chief ideologist for the Khmer Rouge, was hospitalized Sunday and is being treated for acute bronchitis, causing temporary suspension of the trial.

The U.N.-assisted tribunal is trying the pair and former Khmer Rouge foreign minister Ieng Sary for crimes against humanity and other offenses. The communist group's fanatical efforts to realize a utopian society led to the deaths of some 1.7 million people from starvation, disease, overwork and execution from 1975 to 1979.