In 2002, China announced an undisclosed debt cancellation estimated at the time to be between $60 million and $1 billion.
Last week, the leader of a demonstration for housing rights was severely beaten by police, as UN Secretary-General Ban Ki-moon toured.
Cambodia, one of the poorest nations in the world, typically needed aid from both sides to supplement its annual budget and to develop.
China is also a significant investor in Cambodia in garments, textiles, hydropower, agriculture and mining.
Tribunal spokesman Lars Olsen said Wednesday that rape and forced marriage are included in the indictments for Case 002.
Prime Minister Hun Sen told UN Secretary-General Ban Ki-moon he wanted the office head in Cambodia to be sacked.