Tens of thousands of Moroccans marched though the capital Rabat on Sunday to protest against U.N. Secretary General Ban Ki-moon’s position on the Western Sahara dispute and rally support for the king.

Waving portraits of King Mohamed and Moroccan flags, protesters chanted the “The Sahara is ours, the King is ours” as they packed the streets near the parliament building in a rally supported by the government.

Morocco’s government last week accused Ban of no longer being neutral in the Western Sahara conflict, saying he used the word “occupation” to describe Morocco’s presence in the region that has been at the center of a dispute since 1975.

“That was a serious attack on the feelings of all Moroccans, the march shows we are all united in our national cause,” Mbarka Bouida, delegate minister for foreign affairs said, joining the protesters.

State news agency MAP said three million people attended the march, though those figures could not be confirmed. Some protesters said they were bussed for free to the march and said trains had also been free for the day of the rally.

The long-running dispute over the region in the northwest edge of Africa has dragged on since Morocco took control over most of it in 1975 following the withdrawal of former colonial power Spain.

The Polisario Front, which claims the territory belongs to ethnic Sahrawis, fought a rebel war against Morocco until a U.N.-brokered ceasefire in 1991, but the two sides have been deadlocked since that agreement.

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Ban said earlier this month he would restart U.N. efforts to reach a solution after visiting camps in southern Algeria for the Polasario Front leadership and refugees who fled the conflict and who have spent decades there.

The Moroccan government said Ban used the word “occupation” to describe Moroccan annexation of Western Sahara in 1975.

Polisario, backed by Morocco’s regional rival and neighbor Algeria and a number of other African states, wants a referendum promised in the ceasefire agreement on the region’s fate. Morocco says it will not offer more than autonomy for the region, rich in phosphates and possibly offshore oil and gas.

“We came to tell Ban and the world that the Sahara is a red line for us, and we would die for it,” a protester named Salah, who traveled from Oujda area.

Morocco’s king last year insisted only the autonomy plan was acceptable. Rabat invests heavily in the Western Sahara, hoping to calm social unrest and independence claims, and in February announced a $1.85 billion investment plan.