Sydney - Heavy rain brought by tropical cyclones caused flooding in much of north Queensland, news reports said Wednesday.

The sugar-cane town of Ingham north of Townsville was the worst affected with 50 houses under water and hundreds more damaged.

Emergency Services Minister Neil Roberts told national broadcaster ABC some small towns might be cut off for weeks if more rain fell.

"The water seems to be staying up, it's not getting away, so we just hope that (another) cyclone doesn't form," he said.

Roberts said 1 million square kilometres, or 62 per cent of the Queensland state, had been declared a disaster zone.

There are fears that the flooding that has flushed out crocodiles from rivers could result in attacks. Townsfolk have been warned to be on the lookout for crocodiles carried by flooded rivers.

Roberts said the damages may run into millions of dollars because the flooding was the worst he had seen in 30 years.

"But we won't really know the full extent of the damage until the water subsides, so that figure could double, it could treble," he said. (dpa)