 In January 1974, the visit of the Japanese Prime Minister Tanaka Kakuei sparked rioting by students and urban poor in Jakarta.Ostensibly fuelled by resentment of Japanese exploitation of Indonesia's economy, and to start with possibly encouraged tacitly by some Army commanders, this so-called "Malari Affair" soon "got out of hand" and came to express hitherto repressed popular resentment about the growing gap between rich and poor in Indonesian society and the bureaucratic capitalists connected with the regime.Involved as an outspoken human rights activist, Princen was among those who found themselves behind bars in the aftermath, and spent the next two years (1974–1976) in prison.