Cardiff Blues have confirmed that centre Owen Williams has suffered a "significant injury to his cervical vertebrae and spinal cord."
The 22-year-old, who has played four times for Wales, was injured playing for Cardiff Blues at the World Cup 10s on Sunday.
The region said that he underwent an operation on Monday to stabilise a fracture and is currently recovering in hospital in Singapore.
His family and Blues staff are with him in hospital, and arrangements are now being made to arrange his safe transfer home "at an appropriate time."
The region and Williams' family have also thanked hundreds of people who have offered messages of support.
More top news
Swansea must learn the Italian art of defending to continue their climb up the league table, says head coach Francesco Guidolin.
Investigating officers say a driver's intentions were "genuine" when he offered a mother and child a lift during a downpour.
The Wales squad have been put through their paces ahead of tomorrow's Six Nations clash against Scotland in Cardiff.