A person holds a picture of Carlos Manzo, the mayor who was shot dead during a Day of the Dead event, in Uruapan, Mexico, November 2, 2025. REUTERS/Ivan Arias

MEXICO CITY (Reuters) -Mexican authorities on Wednesday announced the arrest of an alleged mastermind in the assassination of a popular opposition mayor, a vocal critic of the government's security policies whose murder has shocked the country and sparked mass protests.

Carlos Manzo, the mayor of Uruapan in the major avocado-producing state of Michoacan, was shot and killed during a public Day of the Dead celebration on November 1 while he was with his family. Manzo had repeatedly accused the federal government of failing to act against organized crime.

Security Minister Omar Garcia Harfuch identified the detainee as Jorge Armando 'N,' withholding his last name as is custom in Mexico. He said investigations linked the man to a criminal group in Michoacan that works for the powerful Jalisco New Generation Cartel.

"This arrest represents a key step in dismantling the criminal structure responsible for this attack," Garcia said at a press conference.

He added that an analysis of cell phones from previously detained suspects "allowed for the identification of a messaging group where the attack was coordinated."

Following the murder, President Claudia Sheinbaum deployed over 10,500 security force members to Michoacan under a new plan to combat extortion and dismantle criminal gangs. Manzo's wife has since succeeded him as mayor of Uruapan.

While several other suspects in the murder have been arrested or killed, including a minor, authorities have not yet clarified the motive for the attack.

(Reporting by Lizbeth Diaz; Writing by Kylie Madry, editing by Deepa Babington)