Passengers were airlifted from a bus stuck in flood waters in Scotland and thousands of homes lost electricity on Wednesday as Storm Frank lashed northern Britain with heavy rains and gales.

Residents could be seen wading through fast-flowing waters in Dumfries where the River Nith broke its banks as two men tried to pump water flowing into the World's End pub and a nearby motorway was submerged.

"We are dealing with a very serious situation," Scottish Environment Minister Aileen McLeod said as officials issued red-alert "danger to life" warnings for Dumfries and another Scottish town, Peebles.

Three hundred homes were evacuated in Peebles.

A Royal Navy helicopter also had to be deployed in Dailly in Ayrshire when a bus was stuck in the water.

"Everyone has now been removed from the bus. Twelve people were airlifted in total," a Police Scotland spokeswoman told AFP, adding that some of the passengers were treated by medical workers at the scene but none needed to go to hospital.

Fast-rising waters disrupted travel across Scotland and the high winds brought down trees and power lines.

"We're starting to get into a few of the communities that have been cut off to see what help and support we can give them," Gavin Stevenson, head of Dumfries and Galloway Council was quoted by the BBC as saying.

"But it has been unprecedented region-wide so we've really relied on our communities to look after themselves until we can get there," he said.

More than 5,500 homes in Scotland were blacked out.

Scotland was bearing the brunt of the impact from Storm Frank after weeks of flooding that have mainly affected Lancashire and Yorkshire in northern England, with water rushing into 6,700 homes.

Elsewhere in Britain on Wednesday, hundreds of people were evacuated in the town of Croston in Lancashire because of flooding, but water levels generally fell in northern England as the clean-up continued.

Flights were also disrupted at Belfast airport and a man was arrested in Yorkshire on suspicion of theft following reports of looting from flooded homes.