A Chinese military unit has been identified as being behind masses of computer hacking cases, according to an American computer security company.
Mandiant said it had investigated hundreds of data breaches since 2004 and Unit 61398 is believed to have stolen data from at least 141 organisations around the world.
It traced the hacking to a building in Shanghai used by the unit.
A BBC correspondent and his camera crew were briefly detained by soldiers when they went to film the facility. They were released only after they handed over their footage.
China denied hacking and questioned the validity of Mandiant's report.
The New York Times reports Unit 61398 has for some time been suspected by the United States of being central to China's cyber espionage programme.