The Balkan region lies on major fault lines and is regularly hit by earthquakes.
A powerful 6.4 magnitude earthquake tore down buildings in central Croatia on Tuesday, striking near the town of Petrinja where rescue teams raced to comb through the rubble.
The tremor, one of the strongest to rock Croatia in recent years, collapsed rooftops in Petrinja, home to some 20,000 people, and left the streets strewn with bricks and other debris.
“We are pulling people from the cars, we don’t know if we have dead or injured,” Darinko Dumbovic, the mayor of Petrinja told regional broadcaster N1.
“There is general panic, people are looking for their loved ones,” he added.
Rescue workers and the army were deployed to search for trapped residents, with no casualties initially reported.
“I’m scared, I can’t reach anyone at home as the phone lines are dead,” one worried woman in Petrinja told N1.
The quake was also felt in the capital Zagreb, 50 kilometres (30 miles) north of the epicentre, where tiles were ripped off roofs and panicked residents gathered streets, according to an AFP reporter.
Electricity was cut in the city centre.
The quake, which struck around 1130 GMT according to the US Geological Survey (USGS), rattled Petrinja just one day after a smaller earthquake struck the town, causing some damage to buildings.
The tremors reverberated across neighbouring countries, including Serbia, Slovenia and as far away as the Austrian capital Vienna.
As a precaution, Slovenia moved to shut down the Krsko nuclear power plan it co-owns with Croatia.
European Union leaders said they were closely following the “devastating earthquake” in member state Croatia.
“We are ready to support,” European Commission chief Ursula von der Leyen wrote on Twitter, adding that the bloc’s civil protection team was “ready to travel to Croatia as soon as the situation allows”.
Charles Michel, president of the European Council, said “our thoughts go out to the injured and frontline workers”.
In March, Zagreb was damaged by a 5.3-magnitude quake, the most powerful to hit the capital decades.