Philippine police used tear gas to disperse about 1,000 anti-US protesters outside the US embassy in Manila on Wednesday, as television news footage showed a patrol van, which had come under attack, driving at demonstrators.

The rally came as President Rodrigo Duterte visits Beijing to strengthen relations with the world's second-largest economy amid deteriorating ties with former colonial power the United States, sparked by his controversial war on illegal drugs.

Police made 29 arrests at the rally while at least 10 people were taken to hospital after being hit by the police van, Renato Reyes, secretary general of left-wing activist group Bayan (Nation), told reporters.

The protesters were calling for the removal of US troops in the southern island of Mindanao.

‘There was absolutely no justification (for the police violence),’ Reyes said. ‘Even as the president avowed an independent foreign policy, Philippine police forces still act as running dogs of the US’

In a series of conflicting statements, Duterte 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 suspected users and pushers. He told Obama to ‘go to hell’ and alluded to severing ties with Washington.

Then, after weeks of anti-American rhetoric, Duterte said the Philippines would maintain its existing defence treaties and its military alliances.

The comments have left Americans and US businesses in the Philippines jittery about their future.