R&B singer Raz-B is currently on life support in a hospital in China ... just one day after he was smashed in the face with a bottle at a nightclub, TMZ has learned.

We spoke to Raz's publicist, Toy Jones, who tells us, "He is in a coma and needs as many prayers as possible."

As we previously reported, the 28-year-old was performing at a club in China on Thursday and was smashed in the face with a glass bottle while trying to break up a fight that erupted in the crowd.

Raz received medical attention hours after the incident --and underwent minor surgery to repair a gash in his lip.

But the next day, sources close to Raz tell us he didn't wake up ... and Raz's backup dancer rushed him to a nearby hospital for treatment.

We're told doctors tested for brain activity and determined the situation was dire. Sources say Raz is breathing from a ventilator ... and has been slipping in and out of consciousness