Croatian soldiers walk next to damaged buildings Tuesday in Petrinja, some 30 miles from the capital, Zagreb, after the town was hit by a 6.4 magnitude earthquake.

Croatian soldiers walk next to damaged buildings Tuesday in Petrinja, some 30 miles from the capital, Zagreb, after the town was hit by a 6.4 magnitude earthquake. / AFP via Getty Images

A powerful earthquake sent shockwaves through Croatia on Tuesday, causing major damage to a town south of the country's capital, Zagreb, and killing at least six, according to news reports quoting officials and residents.

The earthquake, with a magnitude 6.4, struck at about 6:20 a.m. ET., according to the European Mediterranean Seismological Center. The initial tremor was followed by a series of weaker aftershocks.

"This is the largest earthquake to occur in Croatia since the advent of modern seismic instrumentation," according to the U.S. Geological Survey. A slightly smaller earthquake shook Zagreb in 1880.

Tuesday's tremors hit Petrinja the hardest. The central Croatian town has a population of around 24,000.

Buildings collapsed. Debris filled the streets. A woman was trapped under rubble, according to government-owned news website HINA.

Croatian soldiers clean rubble next to damaged buildings Tuesday in Petrinja, a town of about 24,000 residents.

Croatian soldiers clean rubble next to damaged buildings Tuesday in Petrinja, a town of about 24,000 residents. / AFP via Getty Images

A 12-year-old girl was killed in Petrinja and another four people in villages near the town, The Associated Press reported. Officials said at least 20 people were hospitalized — two with serious injuries.

"My town has been completely destroyed. We have dead children," Petrinja Mayor Darinko Dumbovic said, according to the AP. "This is like Hiroshima — half of the city no longer exists."

Dumbovic said town residents were pulling people out of cars and did not know of further deaths or injuries. A kindergarten collapsed, but there were no children inside, he said.

Buildings in Zagreb also reportedly collapsed. No deaths in the city were immediately reported. A nuclear power plant in neighboring Slovenia was automatically shut down due to the earthquake. The temblor was felt as far away as Austria's capital, Vienna, according to Reuters.

Croatian Prime Minister Andrej Plenkovic said he was on his way to the area and had mobilized recovery efforts. European Council President Charles Michel said the European Union "offers its full support and assistance to the people of Croatia."

Tuesday's earthquake comes only a day after the country saw a 5.0 earthquake.

There have been three magnitude 6.0 earthquakes within about 125 miles of the area since 1900, the U.S. Geological Survey said.

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