RABAT: A leading Moroccan activist was arrested Monday alongside other protesters caught up in a wave of rallies that has shaken the country’s northern Rif region for months.

Nasser Zefzafi, who has helped organize months of protests against official abuses and corruption in the north, would be investigated on charges of “threatening national security” and other crimes, state news agency MAP said, citing the general prosecutor.

Protests are rare in the North African kingdom. But tensions have been simmering in Zefzafi’s home city of Al-Hoceima since October when a fishmonger died after being crushed inside a garbage truck while trying to save his fish confiscated by police.

Calls for justice for Mouhcine Fikri, 31, evolved into a grass-roots movement demanding jobs and economic development, with Zefzafi, himself unemployed, emerging as the leader of the Al-Hirak al-Shaabi, or “Popular Movement,” based largely in Al-Hoceima.

The Al-Hoceima protests have been some of the most intense since the 2011 Arab Spring-style unrest that prompted the king to devolve some of his powers to an elected Parliament, though the palace still holds ultimate authority.

Authorities first tried to arrest Zefzafi after he interrupted a sermon during Friday prayers in Al-Hoceima, a government official said. But supporters poured onto the streets and clashed with police as he left the city.

He was detained Monday and transferred with other arrested protesters to the judicial police bureau in Casablanca, MAP said.

Authorities say they have arrested 20 people since Friday. Activists say 28 have been detained. Charges against them include receiving “foreign funding and logistical support to undermine the kingdom’s integrity.”

Protests in solidarity with Zefzafi’s Al-Hirak al-Shaabi were held across the country Sunday night, including in Rabat and Casablanca, and other urban areas.

Saturday, health officials said three policemen were critically injured following the clashes Friday. Activists say several protesters have also been hospitalized.

Monday, it was business as usual in Al-Hoceima, although dozens of families of those arrested gathered outside the courthouse and the police station hoping for news of their relatives.

The mainly ethnically Berber Rif region has long had a tense relationship with Morocco’s central authorities, and was at the heart of Arab Spring-inspired protests in 2011.

The protests subsided following a series of political reforms including constitutional changes that saw King Mohammad VI give up some of his wide-ranging powers.

The current protests in Morocco are calling for greater freedoms and reform of the system and not directly against the king. Morocco has a deeply rooted monarchy – the Muslim world’s longest-serving dynasty.

Interior Minister Abdel-Ouafi Laftit led a large delegation to Al-Hoceima last week, the latest in a series of official trips to the region. Officials have promised increased support for the local economy, in particular the fishing industry.

The unrest comes at a sensitive time, nevertheless, as the kingdom presents itself as a model of economic stability and gradual change and a safe haven for investment in a region torn by violence, Islamist militancy and upheaval.