European Commission President Ursula von der Leyen tweeted: Difficult situation for Croatia: earthquake and coronavirus. Our thoughts are with the Croatian people.
"Stay strong! The EU stands by your side!," von der Leyen tweeted.
European Commissioner for Crisis Management Janez Lenarcic also offered support to Croatia.
"We are closely following the situation on the ground in Croatia after an earthquake hit Zagreb. We are ready to help," Lenarcic said on Twitter.
European Parliament President David Sassoli said, the "European Union is ready to do whatever it can to help" Zagreb after this morning's earthquake.
European Council President Charles Michel too expressed his regret because of the destructive earthquake.
"I just assured (Croatian PM) Andrej Plenkovic that the EU stands with our friends and is ready to offer help and assistance," Michel said on Twitter.
Support and readiness to help Croatia was also expressed by the head of the Social Democrats in the European Parliament, Iratxe Garcia Perez, and the liberal Renew Europe group in the EP.
Two strong earthquakes of 5.3 and 5.1 on the Richter scale hit Zagreb early on Sunday morning, followed by several minor tremors. About a dozen people have been injured, including a 15-year-old girl who is still in critical condition.
Severe damage was caused to Zagreb's centre.