A man and a boy were pulled out alive from a car buried in rubble and sent to a hospital.

The European Mediterranean Seismological Centre said an earthquake of 6.3 magnitude hit 46km southeast of Zagreb.

Initial reports said the earthquake caused wide damage, collapsing roofs, building facades and even entire buildings.

The same area was struck by a 5.2 quake on Monday and several smaller aftershocks had been felt on Tuesday.

The regional N1 television reported live on Tuesday from the town of Petrinja, which was hard-hit in the Monday quake, that a collapsed building had fallen on a car.

The footage showed firefighters trying to remove the debris to reach the car, which was buried underneath.

A man and a small boy were rescued from the car and carried into an ambulance.

In Petrinja, streets were littered with fallen bricks and dust, and many houses were completely destroyed.

The Croatian military has been deployed to help with the rescue operation.

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

He warned people to keep out of potentially shaky, old buildings and move to the newer areas of the city because of the aftershocks.

In Zagreb, people ran out into the streets and parks in fear, with reports of some leaving the city, ignoring a travel ban imposed because of the coronavirus outbreak.

The earthquake was felt throughout the country and in neighbouring Serbia and Bosnia.

It was felt as far away as Graz in southern Austria, the Austria Press Agency reported.

Australian Associated Press