Morocco annexed the former Spanish colony in 1975, and since then it has been the subject of a dispute between Morocco’s government and an independence movement backed by neighboring Algeria.
Moroccan officials had initially said the violence after Sunday’s match had killed one person, and the following day raised the death toll to two.
The match was between Western Sahara side Mouloudia Dakhla and Chabab Mohammadia, a team from a city near Casablanca. An official source in Western Sahara told Reuters two public order officials were among the seven killed.
Moroccan officials said the clashes broke out when supporters leaving the stadium started throwing stones at the opposing team’s supporters.
They said people with criminal records then joined in, attacking passers-by with sticks and knives.
Several people were killed in November last year when Moroccan security forces dismantled a protest camp in Western Sahara, where thousands of residents had gathered to demand better living conditions.
Western Sahara is a sparsely populated tract of desert about the size of Britain. Morocco says the territory should come under its sovereignty, while the exiled Polisario Front says Western Sahara is an independent state.
The Polisario Front waged a guerrilla war against Moroccan forces until the United Nations brokered a cease-fire in 1991. Since then, several rounds of talks have failed to produce a deal on Western Sahara’s status.