New Delhi, Nov. 7 -- The 51st anniversary came as the decades-old conflict enters a new diplomatic phase as a U.N. peacekeeping mission there winds down.

In Laayoune, the largest city in the part of Western Sahara controlled by Morocco, signs of the Green March anniversary were visible across public spaces.

Hundreds of pro-Morocco Sahrawis, an Indigenous group in the Western Sahara, gathered at a central square. Diplomats from Arab and African countries that support Morocco's position also attended the celebrations.

Moroccan flags fluttered in schoolchildren's hands, portraits of King Mohammed VI overlooked roundabouts and public squares, and the national coat of arms adorned major boulevards. Uniformed and plainclothes police officers...