MADRID (REUTERS) - At least eight people have been killed as Storm Gloria has rampaged across eastern Spain, unleashing winds of up to 144 kmh and waves up to 13.5 metres high, officials said on Wednesday (Jan 22).

Three people remained missing four days after Gloria began pummelling the region with torrential rain and heavy snowfall alike.

Rescue officials said the missing included a 25-year-old Briton on the island of Ibiza and a man who fell into the Mediterranean as he tried to moor his boat in Palamos port.

The storm began receding on Wednesday after leaving more than 200,000 people without power at times, destroying rice paddies in the Ebro river delta and triggering weather alerts for three dozen provinces.

Gloria ranks as the worst sea storm since 2003 "and likely of this century", Ms Dani Palacios, head of beach services for Barcelona in the north-east, told local broadcaster BETEVE.

Spanish police said they had found the body of a person in an Alicante river while a source at rescue services said another person died after a building collapsed in nearby Alcoy, likely due to heavy rainfall.

A man working in a greenhouse was killed as hail pounded the structure, a mayor in the province of Almeria told Efe news agency, while authorities in Valencia province blamed the death of a homeless person on frigid cold brought by the storm.

Sea water poured into the Ebro delta, one of Spain's most important wetlands, inundating thousands of hectares of rice plants.

"We can't remember anything similar ever happening," local mayor Lluis Soler told Cadena Ser radio.

"It's dramatic to see how the river has overflowed and the sea has travelled kilometres inland."

Waves in the western Mediterranean hit a record-breaking height of 13.5 metres, port authorities said, slamming into seafront shops and flooding municipalities.

Prime Minister Pedro Sanchez tweeted his "support and solidarity for the families of the victims of Storm Gloria and those suffering its fatal consequences".