People gather with the Kurdish flag during a Syrian Kurdish celebration marking Nowruz, the Persian New Year, on March 21, 2022 in the town of Qahtaniyah in Syria s northeastern Hasakah province close to the border with Turkey. AFP
The IS proto-state -- which once administered millions of people across swathes of Syria and Iraq, on territory roughly the size of Britain -- was declared defeated on March 23, 2019.
The US-backed Syrian Democratic Forces (SDF), which act as the autonomous Kurdish administration's army, led the battle that flushed out the village of Baghouz where IS made its last stand.
The SDF's central command warned in a statement that the countries that provided assistance to the military operation at the time should not turn their backs on the region now.
"The absence of a clear, comprehensive long-term international plan increases human and material losses and allows ISIS to strengthen its organisation," it said, using another acronym for the jihadist group.
IS has not had fixed positions in Iraq or Syria since March 2019 but its remnants have continued to launch hit-and-run guerilla attacks from desert hideouts.
The SDF said a huge attack on a prison in Hasakeh in January was evidence that IS was seeking to expand its operational capabilities.
The battles sparked by the Ghwayran prison break left at least 370 people dead.
According to Britain-based monitoring group the Syrian Observatory for Human Rights, a significant number of IS fighters were sprung free.
The Kurdish forces also blamed those countries that are still reluctant to repatriate their citizens held in camps and prisons for suspected IS members and their relatives.
The autonomous administration has repeatedly complained it did not have the resources to detain the thousands of suspects who poured out of IS territory in the caliphate's dying weeks, let alone to organise trials.