“China’s maritime surveillance ship took law enforcement activities on the illegally operating Vietnamese ships. This was completely justified,” foreign ministry spokeswoman Jiang Yu told reporters.
“We urge the Vietnamese side to stop their activities and refrain from creating trouble.”
On Sunday, Vietnam accused China of expanding the scope of the dispute and demanded that Beijing pay compensation for damages inflicted on a Vietnamese vessel by the Chinese ships.
“China is now causing a misunderstanding with the intention of making an undisputed zone into a zone in dispute,” Vietnamese foreign ministry spokeswoman Nguyen Phuong Nga told reporters.
Beijing and Hanoi have a long-standing dispute in the South China Sea over the sovereignty of the Paracel archipelago and the more southerly Spratlys, both potentially resource-rich outcrops that straddle strategic shipping lanes.
The Vietnam News Agency earlier reported the Chinese vessels had approached the PetroVietnam ship and cut its exploration cables.
A complaint to the Chinese embassy in Hanoi said the incident “seriously violated Vietnam’s sovereignty” and a 1982 United Nations convention on the law of the sea.
China’s increasingly assertive role in the South China Sea has raised tensions with other countries in the region as well as the United States.
The Philippines, Brunei, Malaysia and Taiwan also claim all or part of the Spratlys.