Gavin DeGraw Put in the hospital After Brutal Attack

Singer Gavin DeGraw was put in the hospital after he was viciously attacked by multiple attackers late Sunday evening in New You are able to City

A resource near to Gavin informs TMZ the singer -- who lives in New You are able to City -- was outnumbered by a number of people throughout the attack.

Gavin's repetition states he's still under observation at Bellevue Hospital tonight ... but wouldn't be specific about his injuries.

Gavin continues to be touring with Train and Maroon 5 ... as well as their next stop was scheduled for Tuesday evening in Saratoga Springs, NY. (the story still growing)