Strong winds and heavy rain from storm Bert battered much of Britain again on Sunday, causing "devastating" flooding particularly in Wales, with around 100 flood alerts in place nationwide, authorities said.

In Rhondda Cynon Taf county in south Wales, 200 to 300 homes and buildings were flooded, a local councillor said, prompting the authorities to declare a "major incident" in the area.

A body was found near the river Conwy where search operations took place after a 75-year-old man went missing Saturday after going out to walk his dog, Welsh police said. The victim has yet to be officially identified.

At least three deaths were reported on British roads on Saturday, though they could not immediately be linked to the extreme weather. Amongst them was a victim in the county of Hampshire aged about 60 who was killed after a branch fell on his car. 

Wale's First Minister Eluned Morgan said the impact of the flooding had been "absolutely devastating" in the county, where 80 percent of the usual amount of rain for November fell in just 48 hours.

Storm Bert began pounding Britain and Ireland overnight from Saturday to Sunday, with strong winds, heavy rain and snow interrupting transport links and leaving thousands of properties without power.

Around 100 flood warnings were still in force on Sunday in England, Scotland and Wales, with road closures and train cancellations.

Around 80 properties in England have been flooded, according to the Environment Agency.

Areas on high alert were "the South West, the West Midlands, and the Calder Valley in the North of England due to heavy rain and recent snowmelt", an agency spokesperson said.

Risks of flooding are expected to fall, but persist until Tuesday in parts of England.

The storm triggered wind gusts of up to 110 kilometers per hour, with some London parks and tourist attractions preventively shutting on Sunday.