A police van rammed protesters, injuring several people, during a demonstration outside the US embassy in the Philippines on Wednesday.
The vehicle drove backwards and forwards as tempers flared in Manila where some 1,000 activists were demanding the removal of American troops from the country.
Security forces made at least 29 arrests as they used tear gas to forcefully disperse demonstrators.
The unrest comes amid a torrent of anti-American comments by the Philippines new President Rodrigo Duterte that have cast a cloud over his country’s longstanding relationship with the United States. Duterte did not take well to concerns from Washington and other Western capitals about his deadly war on drugs.
In a series of conflicting statements, he has insulted US President Barack Obama and the US ambassador in Manila for questioning his war on drugs, which has led to the deaths of 2,300 people. He told Obama to “go to hell” and alluded to severing US ties.
But China, where Duterte has arrived for a four day visit, has expressed support for his drug war.
The Philippines leader now says he is considering military exercises with Beijing and Moscow, while vowing war games with American forces are a thing of the past.
Duterte is however hoping to keep his options open.
“Why is Duterte breaking away from the United States? No, I am not breaking away,” Duterte told Chinese television before beginning his trip.
“I just want to be friendly with everybody. So you do not restrain me from doing business in China.”
But Duterte described the visit as “a defining moment”.
He is seeking to mend relations with Beijing amid disputes over territory and waters in the South China Sea.
Strengthened by an international court ruling in the Philippines favour, he has admitted he is seeking Chinese economic aid.
Duterte went to China on Tuesday with at least 200 members of the Philippine business elite to pave the way for what he calls a new commercial alliance. Among the areas expected to be prioritised are financing for Philippine businesses, farm exports, major infrastructure investments and tourism.
The effort to engage China, months after a Hague ruling over South China Sea disputes in favour of the Philippines, marks a reversal in Philippine foreign policy since Duterte took office on June 30.
China has welcomed the shift in tone that has added to strains between the Philippines and the US, even as Duterte has vowed not to surrender any sovereignty to Beijing, which views the maritime ruling as null and void.