A man died after falling into a river on Sunday as Storm Dennis swept across Britain with the army drafted in to help deal with heavy flooding and high winds.

Members of the 4th Battalion Royal Regiment of Scotland erect flood barricades in Ilkley, West Yorkshire on Saturday, as Storm Dennis sweeps in over the UK. Photo: AFP

The man fell into the River Tawe, in south Wales, police said.

The storm also battered much of France, with some 60,000 people suffering power cuts in the northwest of the country and rail traffic disrupted. 

Britain's government weather agency issued a rare red warning for south Wales, saying there was a risk of "significant impacts from flooding" that included a "danger to life from fast flowing water, extensive flooding to property and road closures." 

Police said in a tweet the man who fell into the river was later found dead "further along the river in the Tebanos area."

A record 594 flood warnings and alerts were in place on Sunday, extending from Scotland's River Tweed to Cornwall in southwest England.

Winds of over 150 kilometers per hour (kph) were recorded in Aberdaron, south Wales.

Pictures circulated on social media showed the nearby River Taff bursting its banks, while rescue workers rushed to get people trapped in their homes in Powys to safety.

"The forecast is for very significant levels of rain, especially in the eastern valleys of south Wales," said Jeremy Parr, from government body Natural Resources Wales.

"Impacts could be severe overnight, and everyone should take the warnings extremely seriously," he added.

Police declared major incidents in parts of Wales and England, with landslides also reported.

"Some communities have been cut off... but emergency service workers are working tirelessly to put measures in place to ensure the safety of residents," south Wales police said in a statement.

Roads and railways were badly affected by the downpours and winds, having barely recovered from a similar storm last week.

The defense ministry deployed troops in West Yorkshire, northern England, which suffered badly from flooding caused by last weekend's Storm Ciara.

"Our armed forces are always ready to support local authorities and communities whenever they need it," said defense minister Ben Wallace.

British Airways and easyJet confirmed they had grounded flights, with footage posted online showing a massive Airbus A380 jet being blown about as it attempted to land.

Earlier, two bodies were pulled from rough seas off the south England coast on Saturday as the storm barreled in.

One of the men is assumed to have been the subject of a search triggered when an LPG tanker reported that one of its crew was unaccounted for.

France was also affected by the storm, especially northwestern Brittany where the Finistere and Morbihan regions were temporarily placed on orange alert for rain and flooding, according to the national weather service, Meteo-France.

Electricity provider Enedis said it had deployed 450 staff to restore power to 30,000 homes in Brittany. Power cuts also hit parts of northern and central France.

The storm interrupted two high-speed TGV train services, one stopped by a fallen tree and the other by a power failure, the national rail company SNCF said.

By Sunday evening, Meteo-France said the worst seemed to have passed as winds dropped to below 100 kph.

Several neighboring countries were also affected.

"Winds will be increasing throughout the day on Sunday across Germany, Denmark and southern Sweden," AccuWeather Meteorologist Maura Kelly said earlier Sunday.


Newspaper headline: Storm Dennis batters Britain, France