The latest protest against Andrej Babis was called after Czech prosecutors reopened a probe into Babis's business dealings.
The Social Democrats want the current culture minister to be dismissed but the president is refusing to approve the dismissal, creating a standoff that could topple the government.
The Czech government led by the populist ANO party on Thursday survived a vote of no confidence in parliament after massive protests against Prime Minister Andrej Babis.
The Million Moments for Democracy group is calling for Andrej Babis to quit over allegations that he fraudulently uses his power as Prime Minister to boost his own business interests.
Billionaire Andrej Babiš has been appointed as Czech PM despite large protests about his former Communist links