International Criminal Court (ICC) appeals judges have disqualified chief prosecutor Karim Khan from the war crimes case against former Philippines president Rodrigo Duterte due to a possible conflict of interest.

The ruling is yet another major blow to Khan, who stepped aside in May amid an ongoing UN inquiry into his alleged sexual misconduct. He has now also been barred from taking part in the Duterte prosecution, the only major active case pending at the court, which is already reeling under US-imposed sanctions.

In August, Duterte's defence sought to disqualify Khan, arguing that his involvement in communications to the court from victims of Duterte's war on drugs was a conflict of interest.

The defence said Khan should have no further role in the case because he represented the Philippines Human Rights Commission in naming Duterte as a top suspect and could therefore not conduct an impartial investigation.

Khan had asked the panel of judges to reject the defence request, saying there was "no conflict of interest arising from his representation of the chair of the commission and a group of victims in relation to" communications with the ICC.

The Appeals Chamber on October 2 granted the defence's request, saying in a decision that has not yet been made public that Khan might appear to be biased due to his previous role and so was disqualified from the case.

The ICC office of the prosecutor did not immediately respond to a request for comment.

Duterte, in office from 2016 to 2022, was arrested and taken to The Hague in March on an arrest warrant that linked him to murders committed during his war on drugs in the Philippines, where thousands of alleged narcotics peddlers and users were killed.

He has maintained his arrest was unlawful and tantamount to kidnapping.

The case of the former Philippines president, who is 80 and whose lawyers say he is unfit to stand trial, is currently being handled by deputy prosecutor Mame Mandiaye Niang, who also faces sanctions by Washington due to the court's investigation into alleged war crimes by Israel in Gaza.

ICC judges issued arrest warrants for Israeli Prime Minister Benjamin Netanyahu, former Israeli defence chief Yoav Gallant and Hamas leader Ibrahim al-Masri last November for alleged war crimes and crimes against humanity during the Gaza conflict.

In August, Khan was ordered by judges to recuse himself from an investigation into Venezuela, ruling that his sister-in-law's role as a criminal lawyer representing the government of Venezuelan President Nicolas Maduro was a potential conflict of interest.

In the inquiry into alleged sexual misconduct, Khan's attorneys have denied all allegations of wrongdoing. (Reuters)