Thousands gathered in front of Bulgarian President Rumen Radev's office in Sofia in support of the presidency after prosecutors raided the offices of two of Radev's staff on July 9.
Many protesters saw the showy raids as an attack on Radev and accused prosecutors of deliberately delaying probes into the country's corruption-prone political elites and oligarchs.
Radev last year attempted to block the appointment of the chief prosecutor Ivan Geshev amid popular protests that Geshev would do little to tackle high-level corruption in Bulgaria -- the European Union's most corrupt country according to Transparency International.
The raids came amid rising political tension between Radev and the center-right government of Prime Minister Boyko Borisov ahead of general elections next year.
Radev has often criticized Borisov's government for doing too little to uproot endemic corruption and has blasted prosecutors for cherry-picking their probes and colluding with the government.
Protesters, many of whom were supporters of both left-wing and center-right extra-parliamentary opposition, chanted "Geshev is a disgrace," "Resignation and imprisonment," and "Resign."
Radev came out and thanked protesters for their support, calling for redoubled efforts to rid the government of what he called the mafia.
"Thank you to all of you who are here. I see people from across the political spectrum and this is no accident. The Bulgarian mafia has achieved the impossible: uniting all honest people against them. It rests with all of us to expel the mafia from the executive branch, to expel the mafia from the judiciary, which is used in the most ruthless way for the protection of the very same mafia and for political repression," Radev said.
Prosecutors earlier on July 9 searched the offices of Radev's secretary on legal affairs and anti-corruption and his adviser on security and defense as part of two separate probes into alleged influence peddling and disclosure of state secrets.
Both dignitaries were detained by police for 24 hours. Prosecutors are yet to announce any charges.
Radev's legal secretary, Plamen Uzunov, denied any wrongdoing, and his security adviser, Iliya Milushev, could not be reached for comment.
Radev has declined to comment on the raids directly but accused prosecutors of protecting corrupt individuals.
Geshev has repeatedly denied any political influence and pledged to go after any official suspected of corruption.
However, Bulgaria has yet to jail a single high-ranking official on corruption charges.
The latest political crisis came as the government reintroduced previously lifted coronavirus restrictions after a daily record of 240 new cases was reported on July 9.
The number of recorded infections in the country with some 7 million rose to more than 6,300 on July 9, compared to about 2,700 last month.
So far, Bulgaria has reported 259 deaths.
Bulgaria had already reintroduced compulsory face masks in closed public spaces on June 22.
Prosecutors' Raids On Offices Of Bulgarian Presidential Aides Spark Protests