40 protesters were hurt as police stopped some persons from spraying the walls of the US Embassy with paint Wednesday morning.

Violence erupted at 11:30 am and anti-riot policemen responded with tear gas and water cannon, and a news agency video showed a police patrol vehicle moving back and forth, ramming through several protesters

Police took into custody 21 protesters after the rally where groups were urging the US government to end its intervention in the Philippines and support President Rodrigo Duterte's independent foreign policy.

Renato Reyes, secretary general of Bayan, said among the arrested were lumads, doctors, nurses and health volunteers. Police freed them after a few hours, said Reyes

A one minute and 30 second news video showed a police patrol vehicle running over other protesters as it moved back and forth. The driver was later identified as Police Officer 3 Franklin Kho.

An activist was pinned down by the vehicle but emerged alive. In succeeding parts of the video, policemen with truncheons hitting protesters, which included women on passenger jeepneys.

Among the injured was Sarah Elago, Kabataan partylist representative.

Chief Superintendent Oscar Albayalde, director of the NCR police office, defended the policemen who manned the vehicle.

"They were trying to flip over the patrol car. In the process, the driver extricated the patrol car and inadvertently hit some unruly protesters who sustained minor injuries," said Albayalde.

A total of 32 policemen were injured, said Albayalde.

"It should be emphasized that while we respect the freedom of assembly and speech in exercise of democracy, we cannot tolerate violations of the law and breach in peace and security by people who tends to go beyond it. Democracy does not mean that the law of the land can be violated!," Albayalde said in a text message.

About 700 people from several militant groups, according to the police, include Bagong Alyansang Makabayan, Kabataan Partylist and Sandugo took part in the rally which started past 10 am.

Reyes condemned the violent dispersal which he described as unnecessary.

"There was absolutely no justification for it. Even as the President avowed an independent foreign policy, police forces still act as running dogs of the US," Reyes said in a statement.

The Manila Police District vowed to press cases of illegal assembly, malicious mischief and physical injuries against the protesters.

The Philippine National Police has launched an investigation into the violent dispersal.

"The PNP is now piecing together all facts and circumstances surrounding the violent confrontation between members of the Manila Police District and a group of militant activists in Ermita, Manila," Senior Superintendent Dionardo Carlos, PNP spokesperson, said in a statement.

The investigation will determine criminal and civil liabilities of the leaders and personalities from the ranks of the militant activists that initiated the illegal mass action, said Carlos. Emmanuel Tupas/DMS