The death toll from devastating flash floods in eastern Spain climbed to 158 on Thursday, with rescue teams still searching for those missing in what could become Europe's worst storm-related disaster in over five decades.

"There's a total of 158 people to which must be added dozens and dozens of missing," Angel Victor Torres, minister in charge of cooperation with Spain's regions, told a press conference.

A year's worth of rain fell in eight hours in parts of the Valencia region on Tuesday.