But Vietnamese authorities - who have occasionally allowed demonstrations to vent anger at the country's giant neighbour - warned they would "resolutely" prevent any further outbursts.
China's positioning of an oil rig in waters also claimed by Vietnam has ignited long-simmering enmity between two communist neighbours who have fought territorial skirmishes in past decades, with protests erupting in major cities in recent days and enraged mobs torching foreign-established factories.
However, it urged participants to remain peaceful following the chaos Tuesday and Wednesday.
"Those violent actions created a bad image for patriotic demonstrations and the people of Vietnam; therefore, they must be stopped," said a statement issued on social media late yesterday.
The alliance comprises largely anti-government organisations and is believed to have played a role in stirring the recent protests.
In a text message sent by the government to Vietnamese mobile phone users today, Prime Minister Nguyen Tan Dung said authorities across the country had been ordered to "implement measures to resolutely prevent illegal demonstrations that could cause social and security disorder."
There have been repeated skirmishes near the controversial rig in recent days between Chinese and Vietnamese vessels, including collisions and the use of water cannon.
The violent attacks on Chinese personnel at foreign- invested factories in Vietnam have further aggravated the situation, with China accusing Vietnam's government of a role in the unrest.
Beijing, which has refused to budge on the oil rig, has said two Chinese were killed and more than 100 injured over the past week.
