Philippines President Rodrigo Duterte admitted Thursday he was involved in his government’s extrajudicial killings — a confession that strengthens the international case against him for crimes against humanity.

The extraordinary admission was made as the blunt-spoken 73-year-old defended criticisms of his leadership in a talk at the presidential palace.

“What is my sin? Did I steal even one peso?” he said. “My only sin is the extrajudicial killings.”

The remark contradicted Duterte’s repeated previous denials that the thousands of deaths in the country’s war on drugs have been state-sponsored. Critics called for the remarks to be probed by the International Criminal Court, in their ongoing investigation into allegations of crimes against humanity committed by Duterte in his drugs war.

“This apparent admission by the president himself highlights the urgent need for international investigations,” Minar Pimple, a senior director at Amnesty International, said in a statement.

“This 'playful' comment is a grotesque cruelty at best, and a damning indictment of his government’s murderous campaign at worst.”

Human Rights Watch Asia director Brad Adams said the “admission should erase any doubt about the culpability of the president,” while U.N. Special Rapporteur Agnes Callamard tweeted that Duterte’s comment showed he was responsible for “imposing unthinkable sufferings on 1000s of vulnerable families, emboldening corrupt policing, destroying rule of law.”

In response to the furore, Duterte’s spokesman, Harry Roque, attempted to walk back the comments Friday, saying that his boss wasn’t being “serious.”

"You know the president," Roque told a local radio station. "That's the president being himself, being playful.”

It’s a defense Roque has relied on many times before thanks to Duterte’s long track record of making outlandish, often offensive, claims on the fly.

In November, Duterte boasted in a speech in Vietnam he had stabbed someone to death over a dirty look when he was 16; the previous December, he claimed to have personally shot dead suspected criminals whilst mayor of Davao City in order to set a tough example to local cops.

He also claimed during a rally in 2016 that he had shot a fellow student who had insulted him in his college days — non-fatally this time.

Duterte has also created problems for his spokesman by publically calling Barack Obama a “son of a whore” — and once attempting to joke that he wished he had been first in line to rape a woman who was gang raped and murdered by prison inmates. In February, he told an audience of soldiers they should shoot female rebels in their genitals, which would make them “useless.”

According to the Philippine government’s own statistics, 4,500 people have been killed in anti-drug operations since Duterte came to power, but rights groups say the real number is probably three times higher.

When the ICC confirmed in February it was investigating Duterte over allegations of crimes against humanity in his drug war, the president announced he was withdrawing the country from the Rome Statute, the international agreement that gives the ICC jurisdiction to investigate the country. Experts said the move would not shield Duterte from prosecution, as withdrawal takes a year after the U.N. is notified, and pulling out does not retroactively revoke the court’s jurisdiction.

Duterte later threatened to arrest the ICC prosecutor investigating the allegations against him.

Despite the international criticism of his drugs war and the encroaching legal probe, Duterte reiterated in his speech Thursday that the campaign would not stop. “It will not end,” he said.