HANOI - Anti-China protesters have set more than a dozen factories on fire in Vietnam in the biggest eruption of rage against Beijing for years over the deployment of an oil rig in contested waters.
China expressed "serious concerns" after Vietnamese workers looted goods and attacked offices Tuesday in a rare outburst of public unrest in the authoritarian communist nation.
The protesters targeted manufacturing companies that are owned or managed by Chinese as well as Chinese experts in Binh Duong province, the Vietnam Singapore Industrial Park said in a statement.
There were no reports of casualties but the violence forced several factories to temporarily suspend operations. Many of the those affected were Taiwanese and South Korean-owned plants, possibly mistaken to be Chinese-owned.
Police detained 500 people "caught red-handed looting, stealing and setting fire to factories," Le Xuan Truong of the Binh Duong police told AFP.
Hanoi usually tightly controls demonstrations but recently allowed mass rallies against Beijing.
The riots show the "hazards of nationalist fervour unleashed, particularly in repressive institutional environments such as Vietnam," said Professor Jonathan London at City University of Hong Kong.
"Nationalist sentiment of the intensities we observe in Vietnam are difficult to manage from the top down," London told AFP.
Tens of thousands of workers poured onto the streets Tuesday and a small number of them began looting and attacking security guards and factory management before setting fire to at least 15 factories, the state-run VNExpress website reported.
Videos and images posted on dissident blogs showed thousands of workers - many waving the Vietnamese flag - destroying factory gates, smashing windows and damaging offices.
Export-orientated manufacturing is a key pillar of Vietnam's economy with high-profile firms from electronics giants such as South Korea's Samsung to US sportswear companies Nike and Adidas producing goods in Vietnam.
Calls for restraint
A number of Taiwanese, Japanese and South Korean businesses have reportedly temporarily shut their plants and given workers time off, hanging Vietnamese flags outside their business in a bid to deter looters.
"We made the decision to give our people a day off today as the situation is pretty tense in Vietnam right now," Jerry Shum from Taiwanese footwear manufacturer Yue Yuen told AFP.
"We decided it was the best way to protect our people and premises from any serious damage," said the Hong Kong-based head of investor relations for the company, which supplies to brands such as Nike and Adidas and employs around 100,000 people in Vietnam.
Taiwan condemned the violence and said it had urged Vietnam to guarantee the safety of its nationals.
"We urge the Vietnamese people to exercise restraint and not to take violent and non-rational actions as this would affect Taiwanese businessmen's willingness to invest," Foreign Minister David Lin said.
Hanoi's Ministry of Public Security has deployed rapid-response riot police to the area to reinforce local security staff, VNExpress said.
"There will be serious punishment for those who abused the situation to instigate unrest," local official Tran Van Nam was quoted as saying.
Old rivalry boils over
China and Vietnam are locked in long-standing territorial disputes in the South China Sea over the Paracel and Spratly islands, which both claim.
There have been repeated skirmishes near the controversial oil drilling rig in recent days involving vessels from the two countries, with collisions and the use of water cannon.
Southeast Asian leaders voiced "serious concern" over the worsening sea tensions at a summit on Sunday in Myanmar, after Vietnam and the Philippines led a successful push to put Beijing's territorial assertions high on the agenda.
The Philippines warned on Wednesday that China may be building an airstrip on a reef in the South China Sea as the Asian superpower asserts its claim to most of the strategic area.
Hanoi gave its tacit approval to large anti-China demonstrations Sunday with at least 1,000 people gathering in Hanoi and a similar-sized crowd in Ho Chi Minh City.
The government allowed these rare protests to express their extreme discontent with China but now people have taken this too far, historian Duong Trung Quoc told AFP.
"This is a lesson for the state," he said, adding authorities would likely try to control anti-China demonstrations more closely in future.
Vietnam's communist rulers are also exposed because the real anger underpinning the riots and protests is not simply directed at China, said Adam Fforde, a professor at the University of Victoria in Australia.
Faced with Beijing's assertive stance, the Vietnamese people are also reacting "against a regime that offers no order or leadership capable of the efforts that will be needed" to stand up against China, he said.