Anti-China protesters went on the rampage at an industrial park in southern Vietnam, attacking offices and setting several Chinese factories on fire, authorities said Wednesday.

The unrest -- highly unusual in authoritarian Vietnam -- erupted on Tuesday as thousands of workers staged a walk-out to protest Beijing's deployment of an oil drilling rig in contested waters.

The protesters targeted manufacturing companies that are owned or managed by Chinese, setting three factories on fire, the Vietnam Singapore Industrial Park said in a statement.

There were no reports of casualties.

Reports on Vietnamese social media sites and dissident blogs suggested that the violence had been widespread with some reports suggesting that up to a dozen factories were set ablaze.

Vietnamese police and officials contacted by Agence France Presse 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.