"We are satisfied, but we are not euphoric. We should be patient and wait for the first preliminary results," Dragovan said at the SDP main offices in Zagreb.
According to exit polls from four major cities, published by commercial TV stations, SDP candidates performed well in Zagreb and Rijeka and are likely to retain their mayoral positions.
In Split, independent candidate Zeljko Kerum, who won the largest percent of votes, is followed by SDP candidate Ranko Ostojic and they are likely to compete in a run-off in two weeks' time.
Earlier in the day, some four million Croats voted for mayors, county governors and local law-making bodies in the fifth local elections since Croatia's independence.
Mayors and county heads were directly elected for the first time.