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
The Welsh Government has u-turned on its decision to scrap its youth bus discount scheme.
The rain will become heavy for a time in the west and winds will strengthen, but temperatures remaining mild for the time of year.
Jordan Matthews has been sentenced to life in prison, minimum term 18 years, for the murder of his girlfriend, Xixi Bi.