Abdessalam Yassine, center, who led Morocco’s most powerful religious opposition movement, died Dec. 13. He was 84. (Abdelhak Senna/AFP/Getty Images)

Sheikh Abdessalam Yassine, the charismatic religious leader of Morocco’s largest opposition movement and longtime opponent of two Moroccan kings, died Dec. 13, it was reported from Rabat. He was 84.

A spokeswoman for his movement told Reuters that Mr. Yassine had been suffering from influenza.

Mr. Yassine, who founded Adl wal Ihsan (Justice and Spirituality), accused the monarchy of being corrupt and dictatorial and questioned its claim to religious legitimacy. His spent a decade under house arrest at the hands of Morocco’s former ruler, King Hassan II.

Mr. Yassine refused to accept the king’s title as “commander of the faithful,” and his group went on to become an important part of February 20, the name of a pro-democracy movement that demonstrated in the streets for much of last year for political reform and an end to corruption as part of the region-wide Arab Spring.

The bearded and veiled members of the movement would march side by side with the left-wing and secular activists, calling for less power for the hereditary monarchy and more power for elected officials.

With the election victory of a moderate Islamist opposition party that November, Mr. Yassine’s movement withdrew from protests and has largely remained quiet, apparently giving the new government time to enact reforms.

Formed in 1987, Adl wal Ihsan is officially banned but tolerated, although its members are frequently harassed or arrested by police. The movement advocates an Islamic state and an end to the monarchy, and it professes nonviolence and preaches compassionate Islam.

It has a sizable following, believed to number in the hundreds of thousands. Most Moroccans are Muslims, but religion in this North African nation of 32 million is generally more moderate than in many countries in the Arab world.

Born in Marrakesh in 1928, Mr. Yassine worked for the Education Ministry and wrote two books advocating an Islamic state in Morocco before he shot to fame in 1974 by publishing “Islam or the Deluge,” an open letter to King Hassan II. Mr. Yassine accused the king of corruption and subservience to Western mores, questioned whether he was a true Muslim and called on him to step down.

Mr. Yassine’s pronouncements and more than 20 books, once circulated secretly, are now easier to get because of gradually loosening restrictions and the Internet.

Like most Islamists, Mr. Yassine believed in the supremacy of Islamic civilization and a vision of a Muslim world destined to surpass the West.

Mr. Yassine was well-acquainted with the classics of Western culture, and his main spokeswoman, his daughter Nadia, was educated in France. But he did not want to see Morocco slide toward Westernization. He wrote that “our democracy” is not Western democracy that “begins at pagan Athens and ends in advanced modern societies as a secularist practice, atheistic and immoral.”

His thinking drew from Morocco’s mystical Sufi tradition that put him at odds with the more ultraorthodox Islamists, known as salafis, who have been spreading through North Africa.

Adl wal Ihsan was targeted by King Hassan during the so-called “Years of Lead” in the 1980s and 1990s, when he moved to crush all dissent through violence.

The government detained demonstrators and arrested activists of all stripes for allegedly conspiring to disrupt state security. Many were never charged, and thousands disappeared.

After Hassan died in 1999 and his son assumed the throne as Mohammed VI, Mr. Yassine challenged the new king in a 35-page memorandum, made public the following year, blaming the monarchy for Morocco’s social, economic and political difficulties.

Mohammed released Mr. Yassine from house arrest in May 2000 in a string of gestures aimed at showing a break with the past, but the government has continued to harry Adl wal Ihsan with periodic crackdowns and detentions.

Like other Islamic groups, Mr. Yassine’s movement connected with the poor by providing food, legal aid and other help. That resonates in a country where one-fifth of the population is extremely poor and nearly half are illiterate.

The group never publicly backed a political party, but it is believed that many of the members sympathize with the moderate Islamist Justice and Development Party that dominated last November’s elections.

A complete list of survivors was not available.

— Associated Press