Thousands of protesters have urged Bulgaria's Socialist-led government to resign during a rally in Sofia.
Police said on Sunday that about 15,000 people took part in a rally outside the government building in the capital Sofia to demand a new election. Protesters also gathered outside parliament and in other Bulgarian cities.
Prime Minister Plamen Oresharski's decision to appoint 32-year-old media mogul Delyan Peevski as chief of the powerful national security agency DANS and parliament's rapidity in rubber stamping the nomination angered many people.
Many waved Bulgarian flags and shouted "Mafia!", "Resign!", and "Red garbage!" in what amounted to the biggest rallies in the past three days.
Thousands poured into the streets in protest, sparking fears of a fresh political crisis, just months after anti-poverty demonstrations brought down the previous government.
President Rosen Plevneliev demanded an immediate review of the appointment and said he had lost confidence in the government.
Peevski offered to step down from the post on Saturday and Oresharski said he accepted the resignation.
But protesters were not appeased.
Plamen Oresharski, Bulgaria's prime minister, issued a written statement in which he refused to step down.
"Tabling a resignation now would be an easy personal decision but an extremely irresponsible one due to the danger of new destabilisation in the country," Oresharski said.
The Bulgarian Socialist Party (BSP) formed a governing coalition with the Movement for Rights and Freedoms (DPS), a Turkish minority party, after a snap election last month.
A government led by the Citizens for European Bulgaria (GERB) conservative party resigned in February after mass demonstrations against spending cuts, high energy costs and low salaries in the poorest EU member state.
Anti-government rallies were also held on Sunday in the central city of Plovdiv and in the Black Sea port of Varna.
Protests are to continue on Monday