The earthquake was registered at 11:19 GMT. Its epicentre was located 46 kilometres (28.5 miles) from the Croatian capital of Zagreb, at a depth of 10 kilometres.
The city's authorities called on firefighters and rescuers from all over the country to come to Petrinja, as many houses had been destroyed.
According to the latest data, at least 7 people were killed due to the earthquake, while rescue operations are still underway.
The earthquake is said to be the worst to hit the country in 140 years.