A block of flats in southern Poland has collapsed, killing at least six people, officials say.

Two of those who died were children, firefighters said, and another four people were rescued from the rubble.

Eighteen people are registered as living at the building in the town of Swiebodzice, Radio Poland reports.

Two of the building's floors may have caved in due to a gas explosion, a spokesman for the fire department told AFP news agency.