The BBC's Yvette Austin: "Party-goers were sent screaming in panic"

Both discos were holding so-called polystyrene parties, where people dance ankle-deep in pieces of supposedly fireproof polystyrene.

The most serious fire - in the village of St Agatha near Bad Goisern in the north-west - is believed by police to have broken out after one of the teenagers dropped a cigarette, setting the polystyrene alight.

At least 70 people were taken to hospital from the Joy Disco.

It took firefighters two hours to bring the blaze under control.

Exits blocked

The BBC's Katya Adler: "There are now shocked and anxious parents demanding answers"

Austrian radio quoted rescuers as saying the blaze immediately engulfed the building, and several people were trampled as emergency exits were blocked by slot machines.

"There was panic. People crawled on top of each other," an unnamed rescuer said.

"I tried to pull people out from underneath."

The injured teenagers were taken to three nearby hospitals, where they are being treated for their injuries and for carbon monoxide poisoning caused by breathing in smoke.

Residents gather outside Joy Disco the morning after the fire

Staff say although badly burnt, none of the injured are in a critical condition.

Dozens of others were suffering from shock and were tended to outside the disco by Red Cross workers.

The fire did not spread to neighbouring buildings, but Disco Joy itself is in charred ruins.

The second fire was at a smaller nightspot in Oberndorf, 10 miles north of Salzburg on the German border, with at least 10 people reported injured.

The Austrian press agency reported that the dance floor there too was covered with plastic foam.