A police van rammed into a crowd of anti-American demonstrators Wednesday during a rally outside the U.S. Embassy in the Philippines.
At least three student activists were taken to hospital after being hit by the van.
The protest, which called for the removal of U.S. troops from the country, comes amid strained relations between Washington and Manila.
Philippine President Rodrigo Duterte has in recent months called President Barack Obama a "son of a whore" and told him to "go to hell" while hinting he may scale down U.S. relations in favor of stronger ties with China.
Wednesday's protest is a cause Duterte has backed himself, saying in September that the American forces presented a target for an Islamist group notorious for beheading Westerners.
Video from The Associated Press showed a crowd of around 1,000 demonstrators clashing with riot police outside the embassy building in the Philippine capital.
A police van was seen reversing wildly at speed through the crowd before changing direction and driving forward through the throng. At least one person was run over, although they appeared to be not seriously injured.
The demonstrators hurled red paint at officers carrying shields and at the U.S. government seal outside the embassy compound. Twenty three were arrested, according to the AP.
"There was absolutely no justification for it," protest leader Renato Reyes told the AP. "Even as the president vowed an independent foreign policy, Philippine police forces still act as running dogs of the U.S."
While the clashes raged, Philippine President Duterte was on a visit to China. He has vowed that the long-running territorial dispute over the South China Sea will not stop his country doing trade with Beijing.