As the Philippines confronts one of Asia's worst outbreaks, with over 1.3 million illnesses and over 23,000 deaths, President Rodrigo Duterte has threatened to imprison those who refuse to be vaccinated against the coronavirus.

Following reports of low turnout at many vaccination sites in the capital Manila, Duterte warned in a televised address on Monday, "You choose, vaccine or I will have you incarcerated."

Duterte's comments contradict those of his health officials, who have stated that while the COVID-19 vaccine is recommended, it is optional.

"Don't get me wrong: this country is in trouble," Duterte declared. "I'm really fed up with Filipinos who don't listen to the government."

Philippine officials had fully vaccinated 2.1 million people as of June 20, making slow progress toward the government's goal of immunizing up to 70 million people this year in a country with a population of 110 million.

Duterte, who has been chastised for his hardline stance on the virus, has defended his decision not to reopen schools.

He also took a shot at the International Criminal Court in the same speech, when an ICC prosecutor requested authorization from the court to conduct a complete investigation into the drug war killings in the Philippines.

Duterte, who withdrew the Philippines' participation in the ICC's founding treaty in March 2018, has stated that he will not participate in the investigation, calling the ICC "bullshit."

"Why would I defend myself or face a charge in front of white people? You have to be insane, "After winning the presidency in 2016, Duterte launched an anti-narcotics campaign that has resulted in the deaths of hundreds.

Human rights organizations claim that authorities have executed drug suspects in cold blood, although Duterte claims that those who were killed aggressively resisted capture.

Sought for comment, ICC court spokesperson Fadi El Abdallah said: "The Court is an independent judicial institution, and does not comment on political statements".