The Vietnamese navy carried out four hours of live-fire exercises in the South China Sea on Monday amid an intensifying stand-off with Beijing over disputed island chains.
Tensions between the two sides have risen rapidly in recent weeks following confrontations between Chinese and Vietnamese vessels off the Spratly (in Chinese, Nansha) and Paracel (in Chinese, Changsha) islands.
Vietnam, which has accused China of escalating tensions in the region, carried out a four-hour barrage of live ammunition from a naval vessel 40 kilometers (25 miles) off the central province of Quang Nam.
Naval sources said that a second barrage would follow later on Monday, and that the drills were "routine" and unconnected to recent tension with China.
But regional security analysts said they were likely to escalate tensions around the islands, which are crossed by major shipping lanes and believed to be rich in natural resources.
Show of force?
China's Global Times, a populist newspaper linked to the Communist Party's People's Daily newspaper, described the drills as "a military show of force to defy Beijing."
"Through the flexing of its muscle, Vietnam wants to demonstrate its resolution to maintain its claims on the Nansha Islands," it quoted Zhuang Guotu, director of the Research School of Southeast Asian Studies at Xiamen University, as saying.
Meanwhile, Ji Qiufeng, a professor at the School of Foreign Relations at Nanjing University, told the paper that Vietnam was testing China with the move.
"In response, Beijing needs to make it clear to Vietnam that any challenge to China's sovereignty over the South China Sea cannot succeed," Ji said.
The naval exercises were carried out around 250 kilometers (155 miles) from the Paracel Islands and almost 1,000 kilometres (621 miles) from the Spratlys.
Upholding maritime law
Both Beijing and Hanoi claim sovereignty over the Spratlys, while the Philippines, Malaysia, Brunei, and Taiwan make partial claims to the the maritime region.
Vietnam and China have said they wish to uphold international maritime law in managing the dispute, but analysts say each is using the interpretation that favors its political position.
China's growing military assertiveness has sparked concerns among Beijing's smaller neighbors, and the standoffs have sparked angry anti-China protests in Vietnam.
Protesters held anti-China protests in the capital for the second weekend in a row on Sunday, as more than 100 people demonstrated against what they characterized as bullying by Beijing.
Waving flags and singing patriotic songs, the protesters gathered in a Hanoi park, chanting "Down with China!" and "The Spratlys and Paracels belong to Vietnam."
China had reacted angrily after Vietnam said a Chinese fishing boat rammed cables from an oil exploration vessel inside its exclusive economic zone on Thursday. Chinese fishing boats were also chased away by armed Vietnamese ships, Beijing said.
The Philippines has called on China and Vietnam to stop adding to tensions, while the United States has expressed concern over the situation in the region.
Last weekend, hundreds of people in Vietnam protested in front of Chinese diplomatic missions in Hanoi and in Ho Chi Minh City.
The protests were announced by netizens using social media, including Facebook, text messaging, blogs, and chat forums.
A few days later, more than 200 Vietnamese websites were attacked and some defaced with Chinese flags, according to a state-run Vietnamese Internet security firm.
Reported by Luisetta Mudie.