The three patients are very ill, the head of Zagreb's Fran Mihaljevic Hospital for Infectious Diseases, Alemka Markotic, told a news conference.
Of the three patients, one is a middle-aged person and two are elderly people from the most vulnerable group, Markotic said.
"Fifteen more people have tested positive since 7 am, so now there are 128 infected people in total. Five have recovered, and we have tested a total of 1,779," civil protection official Maja Grba Bujevic told the press conference.
"We are not satisfied with the observance of self-isolation measures. This morning alone, 18 people violated self-isolation measures by entering pharmacies in Zagreb," she said.
The COVID-19 crisis management team is considering the suspension of public transportation services as one of the next measures to contain the spread of the epidemic.
Also, outdoor playgrounds throughout the country were closed on Friday.
Interior Minister Davor Bozinovic called on senior citizens in particular to comply with the recommendations on how to behave during the outbreak of the infection.