A woman found murdered 31 years ago in a river in Belgium has been identified over three decades later thanks to her flower tattoo and an international appeal, Interpol said on Tuesday.

The Lyon-based global police organisation said she was Rita Roberts from Cardiff in Wales and British.

Roberts, found lying against a grate in the river Het Groot Schijn in Antwerp on June 3, 1992, had a tattoo of a black flower with green leaves and the inscription "R'Nick" on her right forearm.

She was 31.

"A family member in the United Kingdom recognised the tattoo on the news and notified Interpol and Belgian authorities," Interpol said in a statement.

The breakthrough followed an international appeal on Interpol's Identify Me web page where police share previously confidential information -- so called Black Notices -- about unsolved cases hoping for input from the public.

The page, launched in May this year, seeks to identify 22 women found dead in recent decades in Germany, Belgium and the Netherlands, Interpol said. Rita Roberts is the first case of the 22 victims to have been identified.

Information volunteered had also brought progress in other cold cases to make progress.

Rita Roberts has been "formally identified" by her family who travelled to Belgium to meet  investigators.

"Whilst the news has been difficult to process, we are incredibly grateful to have uncovered what happened to Rita," the family was quoted in the statement as saying.

- 'A beautiful person' -

Police in Durham, England, said they had supported the family, some of whom live in the area, "during what has been a heartbreaking time for them".

Durham Constabulary called the case "historic".

Durham police quoted a statement from the family, who had asked to remain anonymous, saying  they had last heard from her via a postcard from Belgium in May 1992.

"The news was shocking and heartbreaking. Our passionate, loving, and free-spirited sister was cruelly taken away," the family said.

"There are no words to truly express the grief we felt at that time, and still feel today.

"Rita was a beautiful person who adored travelling. She loved her family, especially her nephews and nieces, and always wanted to have a family of her own," the family said. 

"She had the ability to light up a room, and wherever she went, she was the life and soul of the party. We hope that wherever she is now, she is at peace."

Belgian police hope for further input from the public to clear up the circumstances of Roberts' violent death, it said.

It said that Roberts was believed to have spent time in the Netherlands.

She was 1.70 metres (five foot, seven inches) tall, and wearing a blue-green-purple T-shirt, Adidas jogging trousers and hiking boots when she was found.

"After 31 years an unidentified murdered woman has been given her name back and some closure has been brought to her family," Interpol Secretary General Jurgen Stock said.

"Such cases underline the vital need to connect police worldwide, especially when missing persons are involved."

Interpol is an inter-governmental organisation for police cooperation between the 195 member countries.

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