Rodrigo Duterte has revelled in the “war on drugs” he launched on becoming president of the Philippines two years ago, with its vast and mounting death toll. He has said he personally killed suspected criminals as a city mayor. He has told detained drug suspects: “You want to live longer? Stay in jail.” This week he said that as president “my only sin is the extrajudicial killings”.

Such provocations are inevitably followed by supporters insisting that he is exaggerating or joking. His spokesman called his latest remarks “playful”, though widows and orphans are unlikely to consider them lighthearted. The campaign has left 4,500 people dead even on official statistics, and 12,000 dead according to human rights groups, almost all from the urban poor. In the first year alone, 54 children were killed. Though campaigners say the pace of killing has slowed, it also seems to have shifted away from the capital, Manila – and so away from attention.

Yet Filipinos knew what they were getting when they voted for Mr Duterte in 2016: the “death squad mayor” of Davao warned on the eve of the poll that drug dealers “better get out because I’ll kill you”. Indeed, while he won the presidential race with only 39%, his approval rating, currently at its lowest since he took office, stands at 75%. He has systematically dismantled the checks and balances that might have constrained him, or at least prompted some voters to think again. Senator Leila de Lima, who dared to open an investigation into the killings, was smeared and seized on highly dubious drugs charges. She is still in custody.

This week another critic, Antonio Trillanes, was arrested after an amnesty granted to him was revoked. Government threats, restrictions and an army of trolls have muted the media, despite the courage of individuals. Maria Lourdes Sereno, the country’s top judge, was ousted from the supreme court in May after opposing controversial government proposals. Civil society, too, is suffering.

This makes external pressure all the more crucial. Mr Duterte has given two fingers to critics. When the US halted the sale of assault rifles, Russia stepped in. The admiration of Donald Trump has increased his ability to play the US and China off against each other. And though China and the Philippines have their own disputes – notably over the South China Sea – Japan has cosied up whenever it senses the Manila-Beijing relationship might be cooling.

But the international criminal court has opened a preliminary examination of the killings. There is growing support among members of the UN human rights council for an investigation. Mr Duterte has reacted with defiance and threats. Yet those around him may not be as bullish as they contemplate their future. The national police are particularly sensitive; its chief has blamed “scalawags” in the force for deaths. International pressure could yet have an impact. It must be exerted.