Four girls and a boy aged 10 to 14 have been taken to hospital in Linz, reports the Kronen Zeitung.
The children were sitting around the campfire in Sankt Oswald, around 180 kilometers west of Vienna, when the explosion occurred at around 8 p.m. on Saturday.
The cause was reportedly an object under the fire. Police, who were called to the scene, subsequently found another object - a rifle grenade from World War II - and called in bomb experts.
How the objects ended up at the site is now being investigated. Explosive devices from World War II are occasionally found in Austria, but it is unusual for them to cause personal injury.
