Philippine president Rodrigo Duterte has told the International Criminal Court that he would rather face a firing squad than be jailed if he is found guilty of crimes against humanity.

The ICC has launched a preliminary investigation into the controversial leader to determine whether it can charge him over the deaths of thousands of Filipinos in his infamous war on drugs.

Prosecutor Fatou Bensouda said there were allegations police carried out “extra-judicial” killings as part of a campaign to crack down on the sale and use of illegal drugs in the southeast Asian country.

Mr Duterte has since fired back at the court, encouraging it to investigate his actions and questioning if it had the jurisdiction to charge him.

“I would ask for the rare privilege of talking to you. Just the two of us in the room,” Mr Duterte told a news conference, referring to Mrs Bensouda.

”I welcome you. If you want to find me guilty, go ahead. So be it. Find a country where they kill people with a firing squad and I‘m ready. If you haul me into a rigmarole of trial and trial, no need. Go ahead and proceed in your investigation. Find me guilty, of course. You can do that.”

Around 4,000 mostly urban poor Filipinos have been killed by police in Mr Duterte’s signature campaign, which has drawn concern from the international community.

Activists have claimed the death toll is far higher than reported figures and have made accusations of a systematic cover-up, a claim the government and police forces deny.

The examination is the first formal step the ICC prosecutor takes when considering whether a situation in a member state could eventually lead to charges. The process may take years.

The complaints to the ICC came from a lawyer and two politicians. They include the accounts of two self-confessed hit men.

The most controversial quotes from Rodrigo Duterte Show all 9 1 /9 The most controversial quotes from Rodrigo Duterte The most controversial quotes from Rodrigo Duterte On killing drug addicts “These sons of whores are destroying our children. I warn you, don’t go into that, even if you’re a policeman, because I will really kill you. If you know of any addicts, go ahead and kill them yourself as getting their parents to do it would be too painful” The most controversial quotes from Rodrigo Duterte Message to China “I will go there on my own with a Jet Ski, bringing along with me a [Phillipino] flag and a pole, and once I disembark, I will plant the flag on the runway and tell the Chinese authorities, ‘Kill me’ ” AP The most controversial quotes from Rodrigo Duterte Christmas message to law-breakers “If you do not want to stop, and just continue committing crimes, then this would be your last Merry Christmas” AP The most controversial quotes from Rodrigo Duterte On sex life “I was separated from my wife. I’m not impotent. What am I supposed to do? Let this hang forever? When I take Viagra, it stands up” AFP/Getty Images The most controversial quotes from Rodrigo Duterte On the drugs trade “None of my children are into illegal drugs. But my order is, even if it is a member of my family, ‘kill him'" AP The most controversial quotes from Rodrigo Duterte Insulting the Pope “We were affected by the traffic. It took us five hours. I asked why, they said it was closed. I asked who is coming. They answered, the pope. I wanted to call him: ‘Pope, son of a wh**e, go home. Do not visit us again’” AFP/Getty Images The most controversial quotes from Rodrigo Duterte Joke about rape “I saw her face and I thought, 'What a pity... they raped her, they all lined up. I was mad she was raped but she was so beautiful. I thought, the mayor should have been first” AFP/Getty The most controversial quotes from Rodrigo Duterte Insulting Barack Obama "Mr Obama should be respectful and refrain from throwing questions at me about the killings, or son of a bitch, I will swear at you in that forum" REUTERS The most controversial quotes from Rodrigo Duterte On Abu Sayyaf Islamic militants "If I have to face them, you know I can eat humans. I will really open up your body. Just give me vinegar and salt, and I will eat you. If you annoy me to the fullest... I will eat you alive. Raw" EPA

The men said they killed at Mr Duterte’s behest when he was a city mayor, and public statements he made as president that they say amounted to “shoot-to-kill” orders.

However, Mr Duterte believes the ICC does not have jurisdiction in the Philippines because its accession to the Rome Statute was never announced in the country’s official gazette, a legal requirement.

He also vented his anger at allegations of extrajudicial killings during his campaign, saying the term could not be defined.

“What is extrajudicial killing?” he said, “There is no provision for extrajudicial killing, it is not defined anywhere.”