An anti-China protest was held in Vietnam were around 10 factories were looted and set on fire.
The protest in the southern part of Vietnam marked the most serious riot in the country which has been tightly controlled over the years.
The riot was held in a Singapore-run industrial park late yesterday which was followed by a huge anti-China protest by park employees and those from nearby areas.
Vietnam authorities were confronted by danger when they sought to handle the public anger over China's oil rig deployment in an area in the South China Sea waters that was claimed by Hanoi.
Protesters believed that nearby factories were Chinese but were actually Taiwanese owned. Rioters attacked said factories, reported an industrial factory official who asked not to be named.
The official added that men riding motorbikes drove around the complex while waving Vietnamese flags. Work was also halted during the day, he added.
A foreign diplomat said that there were about 20,000 people who were present during the height of the protest.
Hanoi was infuriated following Beijing's move to deploy a deep sea oil rig near the Paracel Islands. The islands were under Chinese administration but claimed by Vietnam. A fleet of ships were sent out by Hanoi to try and stop the rig. Other Vietnamese boats have also clashed with other Chinese ships sent to guard the oil rig.
The Vietnamese authoritarian government has given a rare permission for protests on the streets against China. This was despite the Hanoi's normal nervousness over spontaneous public gatherings of any sort.
Both China and Vietnam have maintained close ties with one another. However, the May 1 incident caused uproar in Hanoi which had been trying to deal with territorial disputes discreetly.
The protest in Vietnam was the latest of the standoff between China's aggressive pursuit of maritime expansion in the South China Sea despite complaints from smaller nations including Vietnam and the Philippines.
The Philippines' treaty ally, United States, has called the latest action of Beijing "provocative".