Brahim Ghali, the leader of a pro-independence group in Western Sahara, declared war on Morocco Saturday, breaking a decades-long ceasefire, the New York Times reports.

The declaration could reignite an armed struggle and exacerbate years of animosity between Morocco and its neighbour Algeria, which hosts the independence group, the Polisario Front.

The ongoing conflict "has left Morocco controlling about 80 percent of the disputed territory, leaving thousands of Sahrawis living in a protracted displacement situation near the Algerian town of Tindouf," the Times writes.

 The breakdown of the truce comes one day after Morocco conducted a military operation in a UN-patrolled buffer zone in the territory to open a road blocked by Polisario supporters.

Escalating tensions between the groups have drawn concern from the UN, the African Union and nations in Northern Africa and across the Middle East, according to the Times.

UN Secretary General António Guterres said in a statement Friday that he is “determined to do everything possible to remove all obstacles to the resumption of the political process.”