A 6.4 magnitude earthquake has hit Croatia, with reports of at least one death, many injuries and "demolished" towns.

The European-Mediterranean Seismological Centre said the tremor hit 28 miles southeast of the capital, Zagreb.

A 12-year-old child in the town of Petrinja, 31 miles from Zagreb has been killed, according to the N1 news channel.

Petrinja's mayor, Darinko Dumbovic, announced on a local TV broadcast that his town has been "completely destroyed".

"We have dead children," he said.

"Half of the city no longer exists. The city has been demolished, the city is no longer liveable. We need help."

Tomislav Fabijanic, head of emergency medical service in Sisak near Petrinja, said there were many injured in Petrinja and in Sisak.

"There are fractures, there are concussions and some had to be operated on," he said.

At least 20 people went to hospital with injuries, he said, with two seriously hurt.

"The army is here to help. We will have to move some people from Petrinja because it is unsafe to be here," Mr Plenkovic said.

European Commission President Ursula von der Leyen said on Twitter that she spoke with Mr Plenkovic and ordered an envoy to urgently travel to Croatia.

Video footage showed people being rescued from rubble near the epicentre. Other clips showed houses caved in.

The same area was struck by a 5.2 magnitude quake on Monday, killing one person and injuring 27.

Tuesday's tremor could be felt in the capital Zagreb, as well as in neghbouring Bosnia and Serbia - and as far as

The earthquake was felt throughout the country and in neighbouring Serbia, Bosnia and Slovenia - even as far as southern Austria.

After another powerful earthquake in Croatia, the 2nd in the past 2 days, I spoke with Prime Minister @AndrejPlenkovic again.

We are ready to support. I have asked @JanezLenarcic to stand ready to travel to Croatia as soon as the situation allows.

We stand with Croatia.

— Ursula von der Leyen (@vonderleyen) December 29, 2020

Croatian Prime Minister Andrej Plenkovic and other government ministers arrived in Petrinja after the earthquake.

"They are searching through the rubble to see if there is anyone else there,'' Plenkovic said.

"The biggest part of central Petrinja is in a red zone, which means that most of the buildings are not usable."

This is crazy. Another strong earthquake in Croatia, 6.4 this time..#PrayForCroatia pic.twitter.com/aFscEn4va8

— AM (@mareevicka) December 29, 2020

Mr Plenkovic said the army has 500 places ready in barracks to house people, while others will be accommodated in places including nearby hotels.

"No one must stay out in the cold tonight," the PM said.

Slovenia's STA news agency said that the country's sole nuclear power plant was shut down as a precaution.

Video footage showed politicians flee parliament in the capital city of Ljubljana, as the building shook.

Zagreb residents were seen running out of their homes into streets and parks. Many reportedly were leaving the capital, ignoring a travel ban imposed due to the pandemic.

Croatia is prone to earthquakes, but not big ones. The last strong quake struck in the 1990's when the Adriatic coast village of Ston was destroyed.

Croatian seismologist Kresimir Kuk described Tuesday's earthquake as "extremely strong," far stronger than another one that hit Zagreb and nearby areas in the spring.

He warned of potentially strong aftershocks across the Mediterranean country.