BEIJING - China on Thursday "vehemently opposed" a new Vietnamese law asserting sovereignty over islands in disputed waters, the latest escalation in tensions over the resource-rich South China Sea.
The row comes days after an easing in a months-long stand-off between China and the Philippines, but shows the persistent cycle of territorial frictions triggered by what some see as Beijing's growing assertiveness in the area.
Chinese Vice Foreign Minister Zhang Zhijun summoned Ambassador Nguyen Van Tho and told him that Hanoi's new law claiming the contested Paracel and Spratly Islands was a "serious violation" and called for an "immediate correction".
"Vietnam's Maritime Law, declaring sovereignty and jurisdiction over the Paracel and Spratly Islands, is a serious violation of China's territorial sovereignty. China expresses its resolute and vehement opposition," Zhang said, according to a Foreign Ministry statement.
The law was null and void, Zhang said, adding that China would "resolutely defend" its sovereignty.
Vietnam's National Assembly approved the law on Thursday. It says all foreign naval ships passing through the waters must notify Vietnamese authorities.
China has conflicting claims with the Philippines, Vietnam, Brunei, Malaysia and Taiwan across the South China Sea, key shipping lanes thought to contain rich energy reserves. Vietnam and the Philippines have been the most vocal opponents of China's claims.
In the past few days, both Beijing and the Manila cited bad weather after pulling back vessels from a two-month stand-off near the Scarborough Shoal, a contested group of rocks in the sea.
The South China Sea is potentially the biggest flashpoint for confrontation in Asia, and tensions have risen since the United States adopted a policy last year to reinforce its influence in the region.
Chinese Rear Admiral Yin Zhuo told Communist Party mouthpiece the People's Daily website on Thursday that China was well able to fight back in case of any provocation.
"Our navy has the absolute ability and the absolute confidence to use arms to defend our country's sovereignty, territorial integrity and maritime rights ... We're just waiting for the order," he said.