An estimated 4,000 people appeared at an anti-government demonstration in Bratislava on Friday, after new revelations from an investigation into the murder of a journalist in 2018.
Demonstrators listened to speeches from anti-corruption campaigners of the Decent Slovakia Movement.
Several similar rallies were held across the country and abroad.
Investigative reporter Jan Kuciak and his fiancee Martina Kusnirova were murdered at their home in February 2018. New details have since emerged suggesting a link with state bodies.
Mass protests last year forced then-prime minister Robert Fico to resign. His anointed successor Peter Pellegrini has attracted the ire of protesters, who criticise the government's handling of the case
Prosecutors expect to finish their investigation this autumn.