Italian Calzona, 55, had spells as Napoli assistant manager under Maurizio Sarri and Luciano Spalletti.

Calzona will lead Slovakia at Euro 2024 and the country's FA says his deal at Napoli is until the end of the season.

He has a contract with Slovakia until 2025, which would be automatically extended if they qualified for the 2026 World Cup.

Napoli owner Aurelio de Laurentiis thanked Mazzarri for "having helped the team in a tricky period".

They host Barcelona in the first leg of their Champions League last-16 tie on Wednesday.

"The Slovak Football Association is aware this is a non-standard decision that may cause concern among the public," the governing body said.

"However, it also understands the exceptional relationship of Calzona to the club where he worked for a long time and wants to help him in the current difficult situation.

"Calzona has repeatedly declared that the main priority of his activity remains the Slovak national football team and its preparation for Euro 2024."