HANOI, Vietnam (AP) — Several thousand Vietnamese workers have protested at Chinese owned factories to protest Beijing’s deployment of an oil rig in waters claimed by Vietnam.

Photos circulating online showed people pushing over fences at one industrial park and broken windows at a factory.

An executive at one industrial park said the protests began Monday night and by Tuesday had hit four parks.

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

He didn’t give his name because of the sensitivity of the issue.

Vietnam reacted angrily to the deployment of a deep sea oil rig on May 1 close to the Paracel Islands, which are controlled by China but claimed by Hanoi.

Vietnam’s authoritarian government gave its sanction to streets protests over the weekend, but will be concerned about Tuesday’s unrest.