Human Rights Watch urged Moroccan authorities on Friday to free a man handed jail time for calling for protests over the navy's shooting dead of a 22-year-old student.
Soufian al-Nguad posted the call on Facebook after the navy opened fire on a speedboat attempting to carry migrants to Spain in September, killing Hayat Belkacem.
A court in the northern city of Tetouan in October sentenced 29-year-old Nguad, part-owner of an estate agency, to two years in jail and a fine of $2 000 for inciting people to take part in unauthorised protests.
His appeal is underway and another hearing is due on Monday, HRW said.
The New York-based NGO's Middle East and North Africa director Sarah Leah Whitson called the charges against him "illegitimate".
"Soufian al-Nguad did nothing but express his anger and urge protests over the killing of an innocent woman," she said in a statement.
"He should be freed immediately."
Belkacem's killing sparked anger in the North African kingdom, where internet users hailed her as a "martyr" and said her only crime was attempting to leave a miserable life in Morocco to help her family.
The interior ministry said the navy had found the boat off the northern locality of M'diq-Fnideq acting "in a suspicious manner" and refusing to comply with orders.
Three other Moroccans were wounded, one critically, during the assault. The boat's Spanish pilot was arrested.
HRW said there was "no evidence at all to suggest that the passengers were a security risk to anyone".
In a Facebook post, Nguad slammed the "silence" of political figures and urged people to join a protest organised by supporters of a local football team.
HRW slammed the charges against him as an attack on his freedom of expression.
Morocco, a key route for sub-Saharan Africans trying to reach Europe, said it foiled tens of thousands of clandestine bids last year to cross the Mediterranean to Europe.
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