Chinese police in the northeastern city of Harbin have accused the United States National Security Agency (NSA) of launching "advanced" cyberattacks during the Asian Winter Games in February, targeting essential industries.

Police added three alleged NSA agents to a wanted list and also accused the University of California and Virginia Tech of being involved in the attacks after carrying out investigations, according to a report by state news agency Xinhua on Tuesday.

It did not specify how the two American universities were involved.