The commander of the Zagreb fire fighting unit, Siniša Jembrih, said their Ukrainian colleagues told them that 70 firefighting units had been destroyed to date.
Zagreb's firefighters have started a fund-raiser to buy bullet-proof vests for Ukrainian firefighters.
Mayor Tomislav Tomašević attended the show of solidarity, saying Zagreb has thus joined a Eurocities initiative during which some 100 cities held solidarity drives for the people of Ukraine today.
"Once again, we condemn the attack on Ukraine in the strongest terms, we express solidarity and are willing to help," he said, adding that some 200 refugees have been accommodated in Zagreb in two facilities operated by the Interior Ministry and many more with relatives and friends.
Tomašević said a Zagreb Trade Fair pavillion was being prepared in case of a bigger refugee influx.
Mayor expects NATO answers on drone crash
The mayor said he also expected answers on the crash of a drone in a residential area of the capital late on Thursday.
"I'm joining others in the state leadership and expect answers from NATO. How is it possible that such a big aircraft crashes in the middle of the capital of one NATO member state during a war in Europe?," Tomašević said, adding that "we also expect the State Attorney's Office to complete the investigation so that we find out more details, who operated the aircraft and how it ended up here."
The mayor said this incident had significantly jeopardised the people of Zagreb and that it was incredible luck that the drone crashed on grass and that no one was injured.