British human rights lawyer Karim Khan was elected Friday as the new prosecutor of the International Criminal Court, a politically daunting position whose incumbent was slapped with US sanctions. 

Khan, 50, previously led a special UN probe into crimes by the Islamic State extremist group in which he pressed for a trial on the lines of Nuremberg for Nazi war criminals.

More controversially, he also represented late Libyan leader Muammar Gaddafi's son Seif al-Islam.

Khan will be only the third prosecutor of the ICC, taking over in June from Gambian-born Fatou Bensouda, who has outraged Washington through her investigations into the Afghanistan war and the Israeli-Palestinian conflict.

ICC nations failed to reach a consensus choice, triggering a vote in New York among four candidates in which Khan won on the second ballot with 72 votes.

In the first round, he did not win a majority but narrowly edged out Ireland's Fergal Gaynor, who has represented victims before the ICC in the Afghan war investigation and in a case against Kenyan President Uhuru Kenyatta.

The United Nations has 193 member states but only 123 are in the ICC, with the United States, Israel, China and Russia notably absent.

Khan will take on a bulging file of difficult cases at a tribunal whose legitimacy is constantly under attack.

The new prosecutor's first tasks will include deciding the next steps on the probe into war crimes in Afghanistan and the hugely contentious investigation into the 2014 Israel-Palestinian conflict in Gaza.

The ICC is the world's only permanent war crimes court. Hamstrung from the start by the refusal of the United States, Russia and China to join, the court has since faced criticism for having mainly taken on cases from poorer African nations.