The deployment of China's 40-story-tall, billion-dollar oil rig in waters claimed by Vietnam sparked violent protests at Chinese-owned factories across Vietnam on Tuesday, a factory executive and media accounts reported.
The unrest came a day after U.S. Secretary of State John Kerry told China's foreign minister in a telephone call that Beijing's introduction of a platform and several vessels into South China Sea waters disputed with Vietnam was "provocative."
China claims almost the entire South China Sea, rejecting rival claims to parts of it from Vietnam, the Philippines, Taiwan, Malaysia and Brunei.
Kerry "said China's introduction of an oil rig and numerous government vessels in waters disputed with Vietnam was provocative," U.S. State Department spokeswoman Jen Psaki said.
"He urged both sides to de-escalate tensions, ensure safe conduct by their vessels at sea and resolve the dispute through peaceful means in accordance with international law."
Several thousand Vietnamese workers protested at Chinese-owned factories on Tuesday, as anger flared at Beijing's oil rig. Over the weekend, Vietnam's authoritarian government gave rare sanction to street protests against China as way of amplifying its own anger at Beijing. But the protests now appear to be spreading, taking on a violent tinge and directly targeting foreign investment.
Police were present on Tuesday morning, but the protests were continuing, he said. He didn't give his name because of the sensitivity of the issue.
Vietnam reacted angrily to the arrival of the oil rig on May 1 close to the Paracel Islands, which are controlled by China but claimed by Hanoi. Vietnam sent a flotilla of vessels to try and disrupt the drilling, and each country has accused the other of ramming its ships near the disputed Paracel Islands.
China's foreign ministry said there certainly had been provocative moves in the South China Sea, but that China was not the guilty party and repeated that it was the United States' fault for encouraging such behavior.
"We hope that the U.S. side can carefully reflect — if they really hope for the Pacific Ocean to be peaceful — what kind of role do they actually want to play?" spokeswoman Hua Chunying told a daily news briefing.
Hua said that Wang urged Kerry to "objectively and fairly" look at the South China Sea issue and "act and speak cautiously."
In separate remarks to visiting Singapore Foreign Minister K. Shanmugam, Kerry said the United States was deeply concerned by China's "aggressive act" in the dispute.
"We are particularly concerned — all nations that are engaged in navigation and traffic within the South China Sea, the East China Sea, are deeply concerned about this aggressive act," Kerry said in the Monday meeting.
"We want to see a code of conduct created; we want to see this resolved peacefully through the Law of the Sea, through arbitration, through any other means, but not direct confrontation and aggressive action," Kerry added, according to a transcript of his comments released by the State Department.
Speaking to fellow leaders of the Association of Southeast Asian Nations at a summit on Sunday, Prime Minister Nguyen Tan Dung of Vietnam said his country had acted with "utmost restraint" and used all means of dialogue to request China remove the rig.
Dung said China was slandering his country and committing dangerous violations.
However the communiqué issued at the end of the summit by the 10-nation ASEAN group contained no criticism of China.
Al Jazeera and wire services