China has defended its naval harassment of a Vietnamese oil survey ship as legitimate law enforcement activity and urged Vietnam not to create disturbances. Foreign Ministry spokeswoman Jiang Yu on Tuesday said the Vietnamese survey ship had been operating illegally in Chinese-administered waters and that China's action against it was completely justified. Vietnam has filed its protest against China over damage allegedly caused to its seismic survey ship by Chinese petrol vessels. It said the ship was operating well within the country's 370-kilometer exclusive economic zone when it was approached by three Chinese naval vessels. On Sunday, Vietnam accused China of raising tensions and vowed to do everything necessary to protect its territorial integrity. It also demanded compensation for its financial losses.