The US asked China to immediately return its unmanned naval probe in international waters in the South China Sea which it alleged has been unlawfully seized by them. <br/><br/>Pentagon Press Secretary Peter Cook yesterday said that using appropriate government-to-government channels, the Department of Defense has called upon China to immediately return an unmanned underwater vehicle that China seized on December 15 in the South China Sea while it was being recovered by a US Navy oceanographic survey ship. <br/><br/>Senator Ben Cardin, Ranking Member of the Senate Foreign Relations Committee said that China's seizure of an US Navy unmanned scientific research submersible in international waters off the South China Sea is a violation of international law.