A Vietnamese protester holds a banner in a rally against Beijing's deployment of an oil rig in the contested waters of the South China Sea, outside the Chinese Embassy on Sunday. Pic: AP.

HANOI, Vietnam (AP) — An industrial park manger says about 10 factories have been set alight and others looted during anti-China protests in southern Vietnam.

He said the protesters attacked factories in an industrial park that they believed were Chinese

The rioting Tuesday night was some of the most serious public disorder in tightly controlled Vietnam in years.

(MORE: Anti-Chinese sentiment flares in Vietnam amid oil rig dispute)

It shows the danger for authorities as Vietnamese anger mounts over China’s deployment of an oil rig on May 1 in South China Sea waters that Hanoi claims as its own.

The manager would not give his name because of the sensitivity of the issue.