Spain braced for a heavier human toll on Wednesday after 95 people died in flash floods that launched muddy waters through towns, tossed cars and wreaked transport havoc.

Rescuers were expected to find more bodies in the European country's deadliest flood in more than 50 years and three days of official mourning were due to start on Thursday.

Heavy downpours and fierce winds have lashed Spain since the beginning of the week after a storm formed over the Mediterranean Sea, with up to a year's worth of rain falling in just hours in some areas.