The boy's sister Sonu said, he was passing in front of a church when the robbers tried to snatch money from him and stabbed him in the liver.
The boy was rushed to Saket City Hospital, where his condition is serious, as his liver has been punctured, said Binalakshmi Nepram, a Northeast student leader.
This is the fifth attack on Northeast people in Delhi since the death of Arunachal youth Nido Taniam, she said.
The victim is under observation in ICU. A case has been filed under sections 394 and 397 by Mehrauli police, but Nepram insisted that the section 307 (attempt to murder) should also be added in the FIR.
Dr Rakesh Mathur, hospital director, said the boy has an abdominal stab injury and his condition is being monitored for the next 24 to 48 hours.