The International Criminal Court has postponed a pretrial hearing for former Philippine President Rodrigo Duterte, citing concerns about his health.

The 80-year-old was scheduled to appear before the ICC on September 23. He faces charges of crimes against humanity for a deadly anti-drug crackdown during his presidency that rights groups say killed thousands.

However, his lawyers say he is not fit to stand trial. Judges have granted a limited delay to assess whether he can participate in proceedings. The hearing has now been postponed until further notice.

Duterte is the first former Asian president to be charged by the ICC.

What are the charges Duterte faces?

Rodrigo Duterte was arrested in March in Manila and has been held in the ICC's detention unit in the Netherlands since then.

At his first hearing, which he attended via videolink, he appeared weak and barely spoke.

The ICC is investigating mass killings during Duterte's anti-drug crackdowns as mayor of Davao and later as president. Death toll estimates range from more than 6,000 reported by police to 30,000 claimed by rights groups.

Prosecutors claim his drug war was "part of a widespread and systematic attack directed against the civilian population in the Philippines."

Relatives of those killed in Duterte's drug war disappointed

The families of alleged victims of Duterte's drug war also expressed disappointment in the decision. "We expected that Duterte would do this, but the fact that he was able to convince the pretrial chamber to postpone that indefinitely is scary," Kristina Conti, one of the lawyers representing the families, told AFP news agency.

The case has sparked political tensions in Manila, with critics blaming President Ferdinand Marcos Jr. for surrendering Duterte to the ICC. The Marcos and Duterte family dynasties are in a political feud which has polarized the Philippines.  

The court will now decide whether the trial can proceed.

Edited by: Louis Oelofse