A leading human rights group dismissed on Thursday the conviction of a prominent Egyptian political activist as an act of retaliation for his decision to challenge President Abdel Fattah el-Sissi in last year’s presidential election.

On Tuesday, a Cairo misdemeanor court sentenced former presidential hopeful Ahmed Altantawy, along with 22 of his aides, including his campaign manager, to one year in prison on grounds of disseminating un-authortized endorsement forms for his candidacy. The court also barred Altantawy from national elections for the next five years.

"It isn’t just that the authorities are punishing peaceful dissent. By barring Tantawy from running in future elections, the authorities are sending a clear message that no serious challenge to Sisi will be tolerated," said a statement released by Human Rights Watch.

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The New York City-based group urged the Egyptian authorities to drop all charges immediately.

Tantawy, who is at liberty, is still expected to deposit 20,000 Egyptian pounds ($647), which was set as a bail by the court to suspend the sentence while an appeal is filed.

More than 120 members of Altantawy’s presidential campaign have been arrested since last year, according to a local advocacy group.

On Altantawy’s Facebook page, his lawyer Nabeh Elganadi dismissed the trial as fundamentally flawed, accusing the court of ignoring all requests from the defense. "Nothing is right about this trial other than the defendants' names," he wrote.

Last year, Altantawy, who was widely seen as the most viable opposition candidate, dropped out of the presidential race after failing to garner the number of signatures from voters required for a nomination.

At the time, Altantawy accused state security agencies of harassing his staff and supporters to prevent him from reaching the voter threshold for candidacy. El-Sissi was reelected by an overwhelming majority for a third term.

El-Sissi's victory was widely deemed a foregone conclusion — his three opponents were marginal political figures who were rarely seen during the election campaign.

"By continuing the persecution of Tantawy for challenging Sisi, Egyptian authorities have further pulled the mask off a farcical electoral process that ensures one-man rule and annihilates Egyptians’ right to genuine political participation," Amr Magdy, an HRW spokesman said in the group's statement.