Protester Truong Van Dung (C) holds a photo of captain Nguy Van Tha who was killed in the January 1974 Battle of the Paracel Islands, during an anti-China protest in front of the Opera House in Hanoi May 11, 2014.
Anti-China protesters set more than a dozen factories on fire in Vietnam, state media said on Wednesday, in an escalating backlash against Beijing's deployment of an oil rig in contested waters.
Workers looted goods and attacked offices in a rare outburst of public unrest on Tuesday in the authoritarian communist nation, which allowed mass anti-China rallies around Vietnam at the weekend.
The protesters targeted manufacturing companies that are owned or managed by Chinese as well as Chinese workers in Binh Duong province, the Vietnam Singapore Industrial Park said in a statement.
There were no reports of casualties.
Tens of thousands of workers poured onto the streets on 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 and pouring into compounds and causing widespread destruction of property.
A number of Taiwanese, Japanese and South Korean businesses have shut their plants for the day, giving workers the day off, and have hung Vietnamese flags outside their business in a bid to deter looters, VNExpress added.
Hanoi's Ministry of Public Security has deployed rapid-response riot police to the area to reinforce local security staff and prevent further unrest, 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.
Taiwan condemned the violence and said it had urged Vietnam to guarantee the safety of Taiwanese nationals in the area.
"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.
Vietnamese police and officials contacted by AFP repeatedly refused to comment.
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 oil rig in recent days involving vessels from the two countries, with collisions and the use of water cannon.
Vietnamese protesters staged multiple, large anti-China demonstrations Sunday with at least 1,000 people gathering in Hanoi and a similar-sized crowd in Ho Chi Minh City.
Experts say Vietnam's leadership has allowed some public protests to go ahead as a means of expressing extreme discontent with Beijing.